Publications by Department of Mesoscopic Physics
Departments of ISQI | Publications of ISQI
2024 |
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| 69. | Anna Krzyżewska, Anna Dyrdał physica status solidi (RRL) – Rapid Research Letters, 18 (12), pp. 2400123, 2024, ISSN: 1862-6254. @article{Krzyzewska2024Jun, title = {Nonlinear Hall Effect in Isotropic k-Cubed Rashba Model: Berry-Curvature-Dipole Engineering by In-Plane Magnetic Field}, author = {Anna Krzyżewska and Anna Dyrdał}, url = {https://onlinelibrary.wiley.com/doi/10.1002/pssr.202400123 https://arxiv.org/abs/2404.07352}, doi = {10.1002/pssr.202400123}, issn = {1862-6254}, year = {2024}, date = {2024-12-03}, journal = {physica status solidi (RRL) – Rapid Research Letters}, volume = {18}, number = {12}, pages = {2400123}, abstract = {The linear and nonlinear Hall effects in 2D electron gas are considered theoretically within the isotropic k-cubed Rashba model. It is shown that the presence of an out-of-plane external magnetic field or net magnetization is a necessary condition to induce a nonzero Berry curvature in the system, whereas an in-plane magnetic field tunes the Berry curvature leading to the Berry curvature dipole. Interestingly, in the linear response regime, the conductivity is dominated by the intrinsic component (Berry curvature component), whereas the second-order correction to the Hall current (i.e., the conductivity proportional to the external electric field) is dominated by the component independent of the Berry curvature dipole.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The linear and nonlinear Hall effects in 2D electron gas are considered theoretically within the isotropic k-cubed Rashba model. It is shown that the presence of an out-of-plane external magnetic field or net magnetization is a necessary condition to induce a nonzero Berry curvature in the system, whereas an in-plane magnetic field tunes the Berry curvature leading to the Berry curvature dipole. Interestingly, in the linear response regime, the conductivity is dominated by the intrinsic component (Berry curvature component), whereas the second-order correction to the Hall current (i.e., the conductivity proportional to the external electric field) is dominated by the component independent of the Berry curvature dipole. |
| 68. | Stefan Stagraczyński, Pavel Baláž, Mirali Jafari, Józef Barnaś, Anna Dyrdał Scientific Reports, 14 , pp. 25552, 2024. @article{Stagraczynski2024, title = {Magnetic ordering and dynamics in monolayers and bilayers of chromium trihalides: atomistic simulations approach}, author = {Stefan Stagraczyński and Pavel Baláž and Mirali Jafari and Józef Barnaś and Anna Dyrdał}, url = {https://doi.org/10.1038/s41598-024-75501-2}, doi = {10.1038/s41598-024-75501-2}, year = {2024}, date = {2024-10-26}, journal = {Scientific Reports}, volume = {14}, pages = {25552}, abstract = {We analyze magnetic properties of monolayers and bilayers of chromium iodide, CrI3, in two different stacking configurations: AA and rhombohedral ones. Our main focus is on the corresponding Curie temperatures, hysteresis curves, equilibrium spin structures, and spin wave excitations. To obtain all these magnetic characteristic, we employ the atomistic spin dynamics and Monte Carlo simulation techniques. The model Hamiltonian includes isotropic exchange coupling, magnetic anisotropy, and Dzyaloshinskii-Moriya interaction. As the latter interaction is relatively weak in pristine CrI3, we consider a more general case, when the Dzyaloshinskii-Moriya interaction is enhanced externally (e.g. due to gate voltage, mechanical strain, or proximity effects). An important issue of the analysis is the correlation between hysteresis curves and spin configurations in the system, as well as formation of the skyrmion textures.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We analyze magnetic properties of monolayers and bilayers of chromium iodide, CrI3, in two different stacking configurations: AA and rhombohedral ones. Our main focus is on the corresponding Curie temperatures, hysteresis curves, equilibrium spin structures, and spin wave excitations. To obtain all these magnetic characteristic, we employ the atomistic spin dynamics and Monte Carlo simulation techniques. The model Hamiltonian includes isotropic exchange coupling, magnetic anisotropy, and Dzyaloshinskii-Moriya interaction. As the latter interaction is relatively weak in pristine CrI3, we consider a more general case, when the Dzyaloshinskii-Moriya interaction is enhanced externally (e.g. due to gate voltage, mechanical strain, or proximity effects). An important issue of the analysis is the correlation between hysteresis curves and spin configurations in the system, as well as formation of the skyrmion textures. |
| 67. | Izabella Wojciechowska, Anna Dyrdał Intrinsic anomalous, spin and valley Hall effects in ’ex-so-tic’ van-der-Waals structures Scientific Reports, 14 , pp. 23808, 2024. @article{Wojciechowska2024, title = {Intrinsic anomalous, spin and valley Hall effects in ’ex-so-tic’ van-der-Waals structures}, author = {Izabella Wojciechowska and Anna Dyrdał }, url = {https://doi.org/10.1038/s41598-024-74596-x}, doi = {10.1038/s41598-024-74596-x}, year = {2024}, date = {2024-10-11}, journal = {Scientific Reports}, volume = {14}, pages = {23808}, abstract = {We consider the anomalous, spin, valley, and valley spin Hall effects in a pristine graphene-based van-der-Waals (vdW) heterostructure consisting of a bilayer graphene (BLG) sandwiched between a semiconducting van-der-Waals material with strong spin-orbit coupling (e.g., WS2) and a ferromagnetic insulating vdW material (e.g. Cr2Ge2Te2). Due to the exchange proximity effect from one side and spin-orbit proximity effect from the other side of graphene, such a structure is referred to as graphene based ’ex-so-tic’ structure. First, we derive an effective Hamiltonian describing the low-energy states of the structure. Then, using the Green’s function formalism, we obtain analytical results for the Hall conductivities as a function of the Fermi energy and gate voltage. For specific values of these parameters, we find a quantized valley Hall conductivity.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We consider the anomalous, spin, valley, and valley spin Hall effects in a pristine graphene-based van-der-Waals (vdW) heterostructure consisting of a bilayer graphene (BLG) sandwiched between a semiconducting van-der-Waals material with strong spin-orbit coupling (e.g., WS2) and a ferromagnetic insulating vdW material (e.g. Cr2Ge2Te2). Due to the exchange proximity effect from one side and spin-orbit proximity effect from the other side of graphene, such a structure is referred to as graphene based ’ex-so-tic’ structure. First, we derive an effective Hamiltonian describing the low-energy states of the structure. Then, using the Green’s function formalism, we obtain analytical results for the Hall conductivities as a function of the Fermi energy and gate voltage. For specific values of these parameters, we find a quantized valley Hall conductivity. |
| 66. | Peter Zalom, Kacper Wrześniewski, Tomáš Novotný, Ireneusz Weymann Double quantum dot Andreev molecules: Phase diagrams and critical evaluation of effective models Physical Review B, 110 , pp. 134506, 2024. @article{Zalom2024, title = {Double quantum dot Andreev molecules: Phase diagrams and critical evaluation of effective models}, author = {Peter Zalom and Kacper Wrześniewski and Tomáš Novotný and Ireneusz Weymann}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.110.134506}, doi = {10.1103/PhysRevB.110.134506}, year = {2024}, date = {2024-10-07}, journal = {Physical Review B}, volume = {110}, pages = {134506}, abstract = {This paper systematically investigates the phase diagram of a parallel double-quantum-dot Andreev molecule, where the two quantum dots are coupled to a common superconducting lead. Using the numerical renormalization group method, we map out the evolution of the ground state across a wide parameter space of level detunings, size of the superconducting gap, lead couplings, and interdot coupling strength. The intricate phase diagrams feature singlet, doublet, and a relatively uncommon triplet ground states, with the latter being a distinct signature of strong lead-mediated interactions between the quantum dots. We benchmark the applicability of simplified effective models, including the atomic limit and zero-bandwidth approximations, in capturing the complex behavior of this parallel configuration. Our analysis reveals severe limitations of these models, underscoring the necessity for maximal caution when extrapolating beyond their tested validity. In particular, all effective models except for the extended version of the zero-bandwidth approximation failed in reproducing the triplet ground state and made several false predictions. These findings provide crucial insights for interpreting experimental observations and designing superconducting devices based on quantum-dot architectures.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper systematically investigates the phase diagram of a parallel double-quantum-dot Andreev molecule, where the two quantum dots are coupled to a common superconducting lead. Using the numerical renormalization group method, we map out the evolution of the ground state across a wide parameter space of level detunings, size of the superconducting gap, lead couplings, and interdot coupling strength. The intricate phase diagrams feature singlet, doublet, and a relatively uncommon triplet ground states, with the latter being a distinct signature of strong lead-mediated interactions between the quantum dots. We benchmark the applicability of simplified effective models, including the atomic limit and zero-bandwidth approximations, in capturing the complex behavior of this parallel configuration. Our analysis reveals severe limitations of these models, underscoring the necessity for maximal caution when extrapolating beyond their tested validity. In particular, all effective models except for the extended version of the zero-bandwidth approximation failed in reproducing the triplet ground state and made several false predictions. These findings provide crucial insights for interpreting experimental observations and designing superconducting devices based on quantum-dot architectures. |
| 65. | Wojciech Rudziński, Józef Barnaś, Anna Dyrdał Journal of Magnetism and Magnetic Materials, 606 , pp. 172321, 2024. @article{Rudzinski2024b, title = {Spin waves in antiferromagnetically coupled bilayers of transition-metal dichalcogenides with Dzyaloshinskii–Moriya interaction}, author = {Wojciech Rudziński and Józef Barnaś and Anna Dyrdał}, url = {https://doi.org/10.1016/j.jmmm.2024.172321}, doi = {10.1016/j.jmmm.2024.172321}, year = {2024}, date = {2024-09-15}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {606}, pages = {172321}, abstract = {In this paper we analyse quantized spin waves (also referred to as magnons) in bilayers of two-dimensional van der Waals materials, like Vanadium-based dichalcogenides, VX2 (X = S, Se, Te) and other materials of similar symmetry. We assume that the materials exhibit Dzyaloshinskii–Moriya interaction and in-plane easy-axis magnetic anisotropy due to symmetry breaking induced externally (e.g. by strain, gate voltage, proximity effects to an appropriate substrate/oberlayer, etc.). The considerations are limited to a collinear spin ground state, stabilized by a sufficiently strong in-plane magnetic anisotropy. The theoretical analysis is performed within the general spin wave theory based on the Holstein–Primakoff–Bogoliubov transformation. Accordingly, the description takes into account quantum antiferromagnetic fluctuations. However, it is limited to linear spinwave modes. The Dzyaloshinskii–Moriya interaction is shown to modify the spin wave spectrum of the bilayers, making its low energy part qualitatively similar to the electronic spectrum of the Rashba spin–orbit model.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper we analyse quantized spin waves (also referred to as magnons) in bilayers of two-dimensional van der Waals materials, like Vanadium-based dichalcogenides, VX2 (X = S, Se, Te) and other materials of similar symmetry. We assume that the materials exhibit Dzyaloshinskii–Moriya interaction and in-plane easy-axis magnetic anisotropy due to symmetry breaking induced externally (e.g. by strain, gate voltage, proximity effects to an appropriate substrate/oberlayer, etc.). The considerations are limited to a collinear spin ground state, stabilized by a sufficiently strong in-plane magnetic anisotropy. The theoretical analysis is performed within the general spin wave theory based on the Holstein–Primakoff–Bogoliubov transformation. Accordingly, the description takes into account quantum antiferromagnetic fluctuations. However, it is limited to linear spinwave modes. The Dzyaloshinskii–Moriya interaction is shown to modify the spin wave spectrum of the bilayers, making its low energy part qualitatively similar to the electronic spectrum of the Rashba spin–orbit model. |
| 64. | Amir N. Zarezad, Alireza Qaiumzadeh, Józef Barnaś, Anna Dyrdał Topological charge and spin Hall effects due to skyrmions in canted antiferromagnets Physical Review B, 110 (5), pp. 054431, 2024. @article{Zarezad2024b, title = {Topological charge and spin Hall effects due to skyrmions in canted antiferromagnets}, author = {Amir N. Zarezad and Alireza Qaiumzadeh and Józef Barnaś and Anna Dyrdał }, url = {https://doi.org/10.1103/PhysRevB.110.054431}, doi = {10.1103/PhysRevB.110.054431}, year = {2024}, date = {2024-08-20}, journal = {Physical Review B}, volume = {110}, number = {5}, pages = {054431}, abstract = {The topological charge Hall effect (TCHE) and the topological spin Hall effect (TSHE), arising from ferromagnetic (FM) and antiferromagnetic (AFM) skyrmions, respectively, can be elucidated through the emergence of spin-dependent Berry gauge fields that affect the adiabatic flow of electrons within the skyrmion texture. TCHE is absent in systems with parity-time (PT) symmetry, such as collinear AFM systems. In this paper, we theoretically study TCHE and TSHE in a canted antiferromagnet within the diffusive transport regime. Spin canting or weak ferromagnetism in canted AFMs, which break the PT symmetry, may arise, e.g., from strong homogeneous Dzyaloshinskii-Moriya interactions. Using a semiclassical Boltzmann approach, we obtain diffusion equations for the spin and charge accumulations in the presence of finite spin flip and spin-dependent momentum relaxation times. We show that the weak ferromagnetic moment stemming from spin canting and the subsequent breaking of PT symmetry, results in the emergence of both finite TCHE and TSHE in AFM systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The topological charge Hall effect (TCHE) and the topological spin Hall effect (TSHE), arising from ferromagnetic (FM) and antiferromagnetic (AFM) skyrmions, respectively, can be elucidated through the emergence of spin-dependent Berry gauge fields that affect the adiabatic flow of electrons within the skyrmion texture. TCHE is absent in systems with parity-time (PT) symmetry, such as collinear AFM systems. In this paper, we theoretically study TCHE and TSHE in a canted antiferromagnet within the diffusive transport regime. Spin canting or weak ferromagnetism in canted AFMs, which break the PT symmetry, may arise, e.g., from strong homogeneous Dzyaloshinskii-Moriya interactions. Using a semiclassical Boltzmann approach, we obtain diffusion equations for the spin and charge accumulations in the presence of finite spin flip and spin-dependent momentum relaxation times. We show that the weak ferromagnetic moment stemming from spin canting and the subsequent breaking of PT symmetry, results in the emergence of both finite TCHE and TSHE in AFM systems. |
| 63. | Piotr Majek, Ireneusz Weymann Spin-selective transport in a correlated double quantum dot-Majorana wire system Scientific Reports, 14 , pp. 17762, 2024. @article{Majek2024b, title = {Spin-selective transport in a correlated double quantum dot-Majorana wire system}, author = {Piotr Majek and Ireneusz Weymann}, url = {https://www.nature.com/articles/s41598-024-66478-z}, doi = {10.1038/s41598-024-66478-z}, year = {2024}, date = {2024-08-01}, journal = {Scientific Reports}, volume = {14}, pages = {17762}, abstract = {In this work we investigate the spin-dependent transport through a double quantum dot embedded in a ferromagnetic tunnel junction and side attached to a topological superconducting nanowire hosting Majorana zero-energy modes. We focus on the transport regime when the Majorana mode leaks into the double quantum dot competing with the two-stage Kondo effect and the ferromagnetic-contact-induced exchange field. In particular, we determine the system’s spectral properties and analyze the temperature dependence of the spin-resolved linear conductance by means of the numerical renormalization group method. Our study reveals unique signatures of the interplay between the spin-resolved tunneling, the Kondo effect and the Majorana modes, which are visible in the transport characteristics. In particular, we uncover a competing character of the coupling to topological superconductor and that to ferromagnetic leads, which can be observed already for very low spin polarization of the electrodes. This is signaled by an almost complete quenching of the conductance in one of the spin channels which is revealed through perfect conductance spin polarization. Moreover, we show that the conductance spin polarization can change sign depending on the magnitude of spin imbalance in the leads and strength of interaction with topological wire. Thus, our work demonstrates that even minuscule spin polarization of tunneling processes can have large impact on the transport properties of the system.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work we investigate the spin-dependent transport through a double quantum dot embedded in a ferromagnetic tunnel junction and side attached to a topological superconducting nanowire hosting Majorana zero-energy modes. We focus on the transport regime when the Majorana mode leaks into the double quantum dot competing with the two-stage Kondo effect and the ferromagnetic-contact-induced exchange field. In particular, we determine the system’s spectral properties and analyze the temperature dependence of the spin-resolved linear conductance by means of the numerical renormalization group method. Our study reveals unique signatures of the interplay between the spin-resolved tunneling, the Kondo effect and the Majorana modes, which are visible in the transport characteristics. In particular, we uncover a competing character of the coupling to topological superconductor and that to ferromagnetic leads, which can be observed already for very low spin polarization of the electrodes. This is signaled by an almost complete quenching of the conductance in one of the spin channels which is revealed through perfect conductance spin polarization. Moreover, we show that the conductance spin polarization can change sign depending on the magnitude of spin imbalance in the leads and strength of interaction with topological wire. Thus, our work demonstrates that even minuscule spin polarization of tunneling processes can have large impact on the transport properties of the system. |
| 62. | Ryszard Taranko, Kacper Wrześniewski, Ireneusz Weymann, Tadeusz Domański Transient effects in quantum dots contacted via topological superconductor Physical Review B, 110 , pp. 035413, 2024. @article{Taranko2024, title = {Transient effects in quantum dots contacted via topological superconductor}, author = {Ryszard Taranko and Kacper Wrześniewski and Ireneusz Weymann and Tadeusz Domański}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.110.035413}, doi = {10.1103/PhysRevB.110.035413}, year = {2024}, date = {2024-07-10}, journal = {Physical Review B}, volume = {110}, pages = {035413}, abstract = {We investigate gradual development of the quasiparticle states in two quantum dots attached to opposite sides of the topological superconducting nanowire, hosting the boundary modes. Specifically, we explore the nonequilibrium cross-correlations transmitted between these quantum dots via the zero-energy Majorana modes. Our analytical and numerical results reveal the nonlocal features observable in the transient behavior of electron pairing, which subsequently cease while the hybrid structure evolves towards its asymptotic steady-state configuration. We estimate duration of these temporary phenomena. Using the nonperturbative scheme of the time-dependent numerical renormalization group technique we also analyze nonequilibrium signatures of the correlation effects competing with the proximity induced electron pairing. These dynamical processes could manifest themselves in braiding protocols imposed on the topological and/or conventional superconducting quantum bits, using superconducting hybrid nanostructures.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We investigate gradual development of the quasiparticle states in two quantum dots attached to opposite sides of the topological superconducting nanowire, hosting the boundary modes. Specifically, we explore the nonequilibrium cross-correlations transmitted between these quantum dots via the zero-energy Majorana modes. Our analytical and numerical results reveal the nonlocal features observable in the transient behavior of electron pairing, which subsequently cease while the hybrid structure evolves towards its asymptotic steady-state configuration. We estimate duration of these temporary phenomena. Using the nonperturbative scheme of the time-dependent numerical renormalization group technique we also analyze nonequilibrium signatures of the correlation effects competing with the proximity induced electron pairing. These dynamical processes could manifest themselves in braiding protocols imposed on the topological and/or conventional superconducting quantum bits, using superconducting hybrid nanostructures. |
| 61. | Grzegorz Górski, Krzysztof Paweł Wójcik, Jan Barański, Ireneusz Weymann, Tadeusz Domański Nonlocal correlations transmitted between quantum dots via short topological superconductor Scientific Reports, 13 , pp. 13848, 2024. @article{Górski2024, title = {Nonlocal correlations transmitted between quantum dots via short topological superconductor}, author = {Grzegorz Górski and Krzysztof Paweł Wójcik and Jan Barański and Ireneusz Weymann and Tadeusz Domański }, url = {https://www.nature.com/articles/s41598-024-64578-4}, doi = {10.1038/s41598-024-64578-4}, year = {2024}, date = {2024-06-15}, journal = {Scientific Reports}, volume = {13}, pages = {13848}, abstract = {We study the quasiparticle states and nonlocal correlations of a hybrid structure, comprising two quantum dots interconnected through a short-length topological superconducting nanowire hosting overlaping Majorana modes. We show that the hybridization between different components of this setup gives rise to the emergence of molecular states, which are responsible for nonlocal correlations. We inspect the resulting energy structure, focusing on the inter-dependence between the quasiparticles of individual quantum dots. We predict the existence of nonlocal effects, which could be accessed and probed by crossed Andreev reflection spectroscopy. Our study would be relevant to a recent experimental realization of the minimal Kitaev model [T. Dvir et al., Nature 614, 445 (2023)], by considering its hybrid structure with side-attached quantum dots.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We study the quasiparticle states and nonlocal correlations of a hybrid structure, comprising two quantum dots interconnected through a short-length topological superconducting nanowire hosting overlaping Majorana modes. We show that the hybridization between different components of this setup gives rise to the emergence of molecular states, which are responsible for nonlocal correlations. We inspect the resulting energy structure, focusing on the inter-dependence between the quasiparticles of individual quantum dots. We predict the existence of nonlocal effects, which could be accessed and probed by crossed Andreev reflection spectroscopy. Our study would be relevant to a recent experimental realization of the minimal Kitaev model [T. Dvir et al., Nature 614, 445 (2023)], by considering its hybrid structure with side-attached quantum dots. |
| 60. | Verena Brehm, Stefan Stagraczyński, Józef Barnaś, Anna Dyrdał, Alireza Qaiumzadeh Physical Review Materials, 8 (5), pp. 054002, 2024. @article{Brehm2024, title = {Magnon dispersion and spin transport in CrCl3 bilayers under different strain-induced magnetic states}, author = {Verena Brehm and Stefan Stagraczyński and Józef Barnaś and Anna Dyrdał and Alireza Qaiumzadeh}, url = {https://doi.org/10.1103/PhysRevMaterials.8.054002 }, doi = {10.1103/PhysRevMaterials.8.054002}, year = {2024}, date = {2024-05-03}, journal = {Physical Review Materials}, volume = {8}, number = {5}, pages = {054002}, abstract = {Atomically thin van der Waals magnetic materials offer exceptional opportunities to mechanically and electrically manipulate magnetic states and spin textures. The possibility of efficient spin transport in these materials makes them promising for the development of novel nanospintronics technology. Using atomistic spin dynamics simulations, we investigate magnetic ground state, magnon dispersion, critical temperature, and magnon spin transport in CrCl3 bilayers in the absence and presence of compressive and tensile strains. We show that in the presence of mechanical strain, the magnon band gap at the Γ point and the critical temperature of the bilayer are increased. Furthermore, our simulations show that the magnon diffusion length is reduced in the presence of strain. Moreover, by exciting magnons through the spin Seebeck effect and spin Hall-induced torque, we illustrate distinctions between magnon spin transport in the antiferromagnetic state, under compressive strains, and ferromagnetic states, under tensile strains or in the unstrained case.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Atomically thin van der Waals magnetic materials offer exceptional opportunities to mechanically and electrically manipulate magnetic states and spin textures. The possibility of efficient spin transport in these materials makes them promising for the development of novel nanospintronics technology. Using atomistic spin dynamics simulations, we investigate magnetic ground state, magnon dispersion, critical temperature, and magnon spin transport in CrCl3 bilayers in the absence and presence of compressive and tensile strains. We show that in the presence of mechanical strain, the magnon band gap at the Γ point and the critical temperature of the bilayer are increased. Furthermore, our simulations show that the magnon diffusion length is reduced in the presence of strain. Moreover, by exciting magnons through the spin Seebeck effect and spin Hall-induced torque, we illustrate distinctions between magnon spin transport in the antiferromagnetic state, under compressive strains, and ferromagnetic states, under tensile strains or in the unstrained case. |
| 59. | Michał Inglot, Józef Barnaś, Vitalii K. Dugaev, Anna Dyrdał Physical Review B, 109 (13), pp. 134435, 2024. @article{Inglot2024, title = {Localized states at the Rashba spin-orbit domain wall in magnetized graphene: Interplay of Rashba and magnetic domain walls}, author = {Michał Inglot and Józef Barnaś and Vitalii K. Dugaev and Anna Dyrdał}, url = {https://link.aps.org/doi/10.1103/PhysRevB.109.134435}, doi = {10.1103/PhysRevB.109.134435}, year = {2024}, date = {2024-04-23}, journal = {Physical Review B}, volume = {109}, number = {13}, pages = {134435}, abstract = {It is well known that electronic states in graphene with a uniform Rashba spin-orbit interaction and uniform magnetization, e.g., due to exchange coupling to a magnetic substrate, display an energy gap around the Dirac 𝐾 and 𝐾′ points. When the magnetization of graphene is nonuniform and forms a magnetic domain wall, electronic states localized at the wall emerge in the energy gap. In this paper we show that similar localized electronic states appear in the gap when the graphene is uniformly magnetized, while a domain wall appears in the Rashba spin-orbit interaction (i.e., opposite signs of the Rashba parameter on both sides of the wall). These electronic states propagate along the wall and are localized exponentially at the Rashba domain wall. They form narrow and nearly parabolic (at small wave vectors) bands, with relatively large effective electron mass. However, contrary to the magnetic domain wall, these states do not close the energy gap. We also consider the situation when the magnetic domain wall coexists with the Rashba domain wall, and both walls are localized at the same position. Electronic states due to the interplay of both domain walls are determined analytically and it is shown that the electronic states localized at the walls close the gap when a magnetic domain wall (symmetric or asymmetric) exists, independently of the Rashba parameter behavior.}, keywords = {}, pubstate = {published}, tppubtype = {article} } It is well known that electronic states in graphene with a uniform Rashba spin-orbit interaction and uniform magnetization, e.g., due to exchange coupling to a magnetic substrate, display an energy gap around the Dirac 𝐾 and 𝐾′ points. When the magnetization of graphene is nonuniform and forms a magnetic domain wall, electronic states localized at the wall emerge in the energy gap. In this paper we show that similar localized electronic states appear in the gap when the graphene is uniformly magnetized, while a domain wall appears in the Rashba spin-orbit interaction (i.e., opposite signs of the Rashba parameter on both sides of the wall). These electronic states propagate along the wall and are localized exponentially at the Rashba domain wall. They form narrow and nearly parabolic (at small wave vectors) bands, with relatively large effective electron mass. However, contrary to the magnetic domain wall, these states do not close the energy gap. We also consider the situation when the magnetic domain wall coexists with the Rashba domain wall, and both walls are localized at the same position. Electronic states due to the interplay of both domain walls are determined analytically and it is shown that the electronic states localized at the walls close the gap when a magnetic domain wall (symmetric or asymmetric) exists, independently of the Rashba parameter behavior. |
| 58. | Kateryna Boboshko, Anna Dyrdał Physical Review B, 109 (15), pp. 155420, 2024. @article{Boboshko2024, title = {Bilinear magnetoresistance and planar Hall effect in topological insulators: Interplay of scattering on spin-orbital impurities and nonequilibrium spin polarization}, author = {Kateryna Boboshko and Anna Dyrdał}, url = {https://link.aps.org/doi/10.1103/PhysRevB.109.155420}, doi = {10.1103/PhysRevB.109.155420}, year = {2024}, date = {2024-04-15}, journal = {Physical Review B}, volume = {109}, number = {15}, pages = {155420}, abstract = {We have considered theoretically nonlinear transport phenomena known as bilinear magnetoresistance (BMR) and nonlinear planar Hall effect (NPHE) within the effective model describing surface states of a 3D topological insulator. Both phenomena can occur in nonmagnetic materials with strong spin-orbit interaction and reveal a term that depends linearly on the charge current density (external electric field) and in-plane magnetic field. In earlier studies, the physical mechanism of BMR and NPHE was related to scattering on spin-momentum locking inhomogeneities or to the hexagonal warping of Dirac cones. Here, we focus on another mechanism related to scattering on impurities that inherently contain spin-orbit coupling. Using the Green's function formalism and diagramatic method, we have derived analytical results for diagonal and transverse conductivities and determined nonlinear signals. The analytical and numerical results on BMR and NPHE indicate the possibility of determining the material constants, such as the Fermi wave vector and spin-orbit coupling parameter, by simple magnetotransport measurements.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We have considered theoretically nonlinear transport phenomena known as bilinear magnetoresistance (BMR) and nonlinear planar Hall effect (NPHE) within the effective model describing surface states of a 3D topological insulator. Both phenomena can occur in nonmagnetic materials with strong spin-orbit interaction and reveal a term that depends linearly on the charge current density (external electric field) and in-plane magnetic field. In earlier studies, the physical mechanism of BMR and NPHE was related to scattering on spin-momentum locking inhomogeneities or to the hexagonal warping of Dirac cones. Here, we focus on another mechanism related to scattering on impurities that inherently contain spin-orbit coupling. Using the Green's function formalism and diagramatic method, we have derived analytical results for diagonal and transverse conductivities and determined nonlinear signals. The analytical and numerical results on BMR and NPHE indicate the possibility of determining the material constants, such as the Fermi wave vector and spin-orbit coupling parameter, by simple magnetotransport measurements. |
| 57. | Piotr Trocha, Thibaut Jonckheere, Jérôme Rech, Thierry Martin Journal of Magnetism and Magnetic Materials, 596 , pp. 171922, 2024. @article{Trocha2024, title = {Out-of-equilibrium voltage and thermal bias response of a quantum dot hybrid system coupled to topological superconductor}, author = {Piotr Trocha and Thibaut Jonckheere and Jérôme Rech and Thierry Martin}, url = {https://www.sciencedirect.com/science/article/pii/S0304885324002130?via%3Dihub}, doi = {/10.1016/j.jmmm.2024.171922}, year = {2024}, date = {2024-04-15}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {596}, pages = {171922}, abstract = {We investigate theoretically the out-of-equilibrium transport properties of a single-level quantum dot coupled to a normal metal electrode and attached to a topological superconductor. Both voltage and thermal bias responses of the system in the nonequilibrium regime are studied. To obtain transport characteristics we used the nonequilibrium Green’s function approach. Particularly, we calculated the current and the corresponding differential conductance in two distinct cases. In the former situation, the charge current is induced by applying a bias voltage, whereas in the latter case it is generated by setting a temperature difference between the leads with no bias voltage. Moreover, strong diode effect in thermally generated current is found and non-equilibrium thermopower is analyzed.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We investigate theoretically the out-of-equilibrium transport properties of a single-level quantum dot coupled to a normal metal electrode and attached to a topological superconductor. Both voltage and thermal bias responses of the system in the nonequilibrium regime are studied. To obtain transport characteristics we used the nonequilibrium Green’s function approach. Particularly, we calculated the current and the corresponding differential conductance in two distinct cases. In the former situation, the charge current is induced by applying a bias voltage, whereas in the latter case it is generated by setting a temperature difference between the leads with no bias voltage. Moreover, strong diode effect in thermally generated current is found and non-equilibrium thermopower is analyzed. |
| 56. | Kacper Wrześniewski, Ireneusz Weymann Scientific Reports, 14 (7815), 2024. @article{Wrześniewski2024, title = {Cross-correlations between currents and tunnel magnetoresistance in interacting double quantum dot-Majorana wire system}, author = {Kacper Wrześniewski and Ireneusz Weymann }, url = {https://link.springer.com/article/10.1038/s41598-024-58344-9}, doi = {10.1038/s41598-024-58344-9}, year = {2024}, date = {2024-04-03}, journal = {Scientific Reports}, volume = {14}, number = {7815}, abstract = {We theoretically investigate the spin and charge transport properties of a double quantum dot coupled to distinct edges of the nanowire hosting Majorana zero-energy modes. The focus is on the analysis of the currents flowing through the left and right junctions and their cross-correlations. We show that the system reveals very different transport properties depending on the detuning protocol of the quantum dot energy levels. For the symmetric detuning, the current dependencies reveal only two maxima associated with resonant tunneling, and currents in the left and right arms of the system reveal weak positive cross-correlations. On the other hand, for antisymmetric detuning, the flow of electrons into drains is maximized and strongly correlated in one bias voltage direction, while for the opposite bias direction a spin blockade is predicted. Furthermore, we observe a suppression of the current cross-correlations at a highly symmetric detuning point, indicating the involvement of the Majorana zero-energy modes in the transport processes. To gain insight into the role of the spin polarization of the Majorana edge states, we analyze the spin-dependent transport characteristics by considering the relationship between the spin canting angle, which describes the coupling of the Majorana modes to the spin of the quantum dots, and the magnetic configurations of the ferromagnetic drains. Moreover, we examine the non-local zero bias anomaly in the differential conductance, detailed analysis of which revealed a specific operational mode of the device that can facilitate the identification of the Majorana presence in the quantum dot-Majorana wire system. Finally, we also consider the transport properties in different magnetic configurations of the system and discuss the behavior of the associated tunnel magnetoresistance.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We theoretically investigate the spin and charge transport properties of a double quantum dot coupled to distinct edges of the nanowire hosting Majorana zero-energy modes. The focus is on the analysis of the currents flowing through the left and right junctions and their cross-correlations. We show that the system reveals very different transport properties depending on the detuning protocol of the quantum dot energy levels. For the symmetric detuning, the current dependencies reveal only two maxima associated with resonant tunneling, and currents in the left and right arms of the system reveal weak positive cross-correlations. On the other hand, for antisymmetric detuning, the flow of electrons into drains is maximized and strongly correlated in one bias voltage direction, while for the opposite bias direction a spin blockade is predicted. Furthermore, we observe a suppression of the current cross-correlations at a highly symmetric detuning point, indicating the involvement of the Majorana zero-energy modes in the transport processes. To gain insight into the role of the spin polarization of the Majorana edge states, we analyze the spin-dependent transport characteristics by considering the relationship between the spin canting angle, which describes the coupling of the Majorana modes to the spin of the quantum dots, and the magnetic configurations of the ferromagnetic drains. Moreover, we examine the non-local zero bias anomaly in the differential conductance, detailed analysis of which revealed a specific operational mode of the device that can facilitate the identification of the Majorana presence in the quantum dot-Majorana wire system. Finally, we also consider the transport properties in different magnetic configurations of the system and discuss the behavior of the associated tunnel magnetoresistance. |
| 55. | Amir N. Zarezad, Józef Barnaś, Alireza Qaiumzadeh, Anna Dyrdał Bilinear Planar Hall Effect in Topological Insulators Due to Spin-Momentum Locking Inhomogeneity physica status solidi (RRL) – Rapid Research Letters, 18 (3), pp. 2200483, 2024. @article{Zarezad2024c, title = {Bilinear Planar Hall Effect in Topological Insulators Due to Spin-Momentum Locking Inhomogeneity}, author = {Amir N. Zarezad and Józef Barnaś and Alireza Qaiumzadeh and Anna Dyrdał}, url = {https://doi.org/10.1002/pssr.202200483}, doi = {10.1002/pssr.202200483}, year = {2024}, date = {2024-03-13}, journal = {physica status solidi (RRL) – Rapid Research Letters}, volume = {18}, number = {3}, pages = {2200483}, abstract = {Herein, the effect of spin-momentum locking inhomogeneity on the planar Hall effect in topological insulators (TIs) is studied. Using the minimal model describing surface states of 3D TIs and semiclassical Boltzmann formalism, the planar Hall conductivity (PHC) within the generalized relaxation time approximation is derived. Herein, it is found that the total PHC consists of linear and nonlinear (in electric field) components. The linear term is a conventional PHC which scales quadratically with an external magnetic field, whereas the nonlinear term reveals bilinear behavior, that is, changes its sign when either charge current density or in-plane magnetic-field orientation is reversed. It is shown that the emergent nonlinear planar Hall effect is a consequence of spin-momentum locking inhomogeneity in the TIs with isotropic energy dispersion, and dominates over the conventional planar Hall effect.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Herein, the effect of spin-momentum locking inhomogeneity on the planar Hall effect in topological insulators (TIs) is studied. Using the minimal model describing surface states of 3D TIs and semiclassical Boltzmann formalism, the planar Hall conductivity (PHC) within the generalized relaxation time approximation is derived. Herein, it is found that the total PHC consists of linear and nonlinear (in electric field) components. The linear term is a conventional PHC which scales quadratically with an external magnetic field, whereas the nonlinear term reveals bilinear behavior, that is, changes its sign when either charge current density or in-plane magnetic-field orientation is reversed. It is shown that the emergent nonlinear planar Hall effect is a consequence of spin-momentum locking inhomogeneity in the TIs with isotropic energy dispersion, and dominates over the conventional planar Hall effect. |
| 54. | Anand Manaparambil, Ireneusz Weymann Spin-resolved nonequilibrium thermopower of asymmetric nanojunctions Phys. Rev. B, 109 , pp. 115402, 2024. @article{Manaparambil2024b, title = {Spin-resolved nonequilibrium thermopower of asymmetric nanojunctions}, author = {Anand Manaparambil and Ireneusz Weymann}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.109.115402}, doi = {10.1103/PhysRevB.109.115402}, year = {2024}, date = {2024-03-04}, journal = {Phys. Rev. B}, volume = {109}, pages = { 115402}, abstract = {The spin-resolved thermoelectric transport properties of correlated nanoscale junctions, consisting of a quantum dot/molecule asymmetrically coupled to external ferromagnetic contacts, are studied theoretically in the far-from-equilibrium regime. One of the leads is assumed to be strongly coupled to the quantum dot resulting in the development of the Kondo effect. The spin-dependent current flowing through the system, as well as the thermoelectric properties, are calculated by performing a perturbation expansion with respect to the weakly coupled electrode, while the Kondo correlations are captured accurately by using the numerical renormalization group method. In particular, we determine the differential and nonequilibrium Seebeck effects of the considered system in different magnetic configurations and uncover the crucial role of spin-dependent tunneling on the device performance. Moreover, by allowing for the spin accumulation in the leads, which gives rise to finite spin bias, we shed light on the behavior of the nonequilibrium spin Seebeck effect. In particular, we predict new sign changes of the spin-resolved Seebeck effect in the nonlinear response regime, which stem from the interplay of exchange field and finite voltage and temperature gradients.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The spin-resolved thermoelectric transport properties of correlated nanoscale junctions, consisting of a quantum dot/molecule asymmetrically coupled to external ferromagnetic contacts, are studied theoretically in the far-from-equilibrium regime. One of the leads is assumed to be strongly coupled to the quantum dot resulting in the development of the Kondo effect. The spin-dependent current flowing through the system, as well as the thermoelectric properties, are calculated by performing a perturbation expansion with respect to the weakly coupled electrode, while the Kondo correlations are captured accurately by using the numerical renormalization group method. In particular, we determine the differential and nonequilibrium Seebeck effects of the considered system in different magnetic configurations and uncover the crucial role of spin-dependent tunneling on the device performance. Moreover, by allowing for the spin accumulation in the leads, which gives rise to finite spin bias, we shed light on the behavior of the nonequilibrium spin Seebeck effect. In particular, we predict new sign changes of the spin-resolved Seebeck effect in the nonlinear response regime, which stem from the interplay of exchange field and finite voltage and temperature gradients. |
| 53. | Piotr Pigoń, Anna Dyrdał Journal of Magnetism and Magnetic Materials, 593 , pp. 171795, 2024. @article{Pigon2024, title = {Electronic and topological properties of a topological insulator sandwiched between ferromagnetic insulators}, author = {Piotr Pigoń and Anna Dyrdał }, url = {https://doi.org/10.1016/j.jmmm.2024.171795}, doi = {10.1016/j.jmmm.2024.171795}, year = {2024}, date = {2024-03-01}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {593}, pages = {171795}, abstract = {We consider a film of a topological insulator (TI) sandwiched between two ferromagnetic (FM) layers. The system is additionally under an external gate voltage. The surface electron states of TI are magnetized due to the magnetic proximity effect to the ferromagnetic layers. The magnetization of ferromagnetic layers can be changed by applying an external magnetic field or by varying thickness of the topological insulator (owing to the interlayer exchange coupling). The change in the magnetic configuration of the system affects the transport properties of the surface electronic states. Using the Green function formalism, we calculate spin polarization, anomalous Hall effect, and magnetoresistance of the system. We show, among others, that by tuning the gate voltage and magnetizations of the top and bottom FM layers, one can observe the topological transition to the quantum anomalous Hall state.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We consider a film of a topological insulator (TI) sandwiched between two ferromagnetic (FM) layers. The system is additionally under an external gate voltage. The surface electron states of TI are magnetized due to the magnetic proximity effect to the ferromagnetic layers. The magnetization of ferromagnetic layers can be changed by applying an external magnetic field or by varying thickness of the topological insulator (owing to the interlayer exchange coupling). The change in the magnetic configuration of the system affects the transport properties of the surface electronic states. Using the Green function formalism, we calculate spin polarization, anomalous Hall effect, and magnetoresistance of the system. We show, among others, that by tuning the gate voltage and magnetizations of the top and bottom FM layers, one can observe the topological transition to the quantum anomalous Hall state. |
| 52. | Vrishali Sonar, Piotr Trocha Non-local thermoelectric transport in multi-terminal quantum dot hybrid system Journal of Magnetism and Magnetic Materials, 593 , pp. 171745, 2024. @article{Sonar2024, title = {Non-local thermoelectric transport in multi-terminal quantum dot hybrid system}, author = {Vrishali Sonar and Piotr Trocha}, url = {https://www.sciencedirect.com/science/article/pii/S0304885324000350?via%3Dihub}, doi = {10.1016/j.jmmm.2024.171745}, year = {2024}, date = {2024-03-01}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {593}, pages = {171745}, abstract = {The heat and charge transport is studied in a hybrid multi-terminal device consisting of one metallic, one ferromagnetic and a superconducting lead coupled to quantum dot. The basic thermoelectric properties of the system are examined using non-equilibrium Green’s function method with finite on-dot Coulomb repulsion within Hubbard-I approximation. Local and non-local transport coefficients including electrical and thermal conductance, Seebeck coefficient calculated in the linear response regime. Main objective is to analyze effect of superconductor coupling and ferromagnet’s spin polarization on thermoelectric transport and how ferromagnetic lead modifies it. We also studied the role of different electron tunneling types, i. e. Andreev reflection, quasi-particle and normal single particle tunneling processes on thermoelectric properties of the considered system.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The heat and charge transport is studied in a hybrid multi-terminal device consisting of one metallic, one ferromagnetic and a superconducting lead coupled to quantum dot. The basic thermoelectric properties of the system are examined using non-equilibrium Green’s function method with finite on-dot Coulomb repulsion within Hubbard-I approximation. Local and non-local transport coefficients including electrical and thermal conductance, Seebeck coefficient calculated in the linear response regime. Main objective is to analyze effect of superconductor coupling and ferromagnet’s spin polarization on thermoelectric transport and how ferromagnetic lead modifies it. We also studied the role of different electron tunneling types, i. e. Andreev reflection, quasi-particle and normal single particle tunneling processes on thermoelectric properties of the considered system. |
| 51. | Krzysztof P. Wójcik, Tadeusz Domański, Ireneusz Weymann Signatures of Kondo-Majorana interplay in ac response Phys. Rev. B, 109 , pp. 075432, 2024. @article{Wójcik2024, title = {Signatures of Kondo-Majorana interplay in ac response}, author = {Krzysztof P. Wójcik and Tadeusz Domański and Ireneusz Weymann}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.109.075432}, doi = {10.1103/PhysRevB.109.075432}, year = {2024}, date = {2024-02-26}, journal = {Phys. Rev. B}, volume = {109}, pages = {075432}, abstract = {We analyze dynamical transport properties of a hybrid nanostructure, comprising a correlated quantum dot embedded between the source and drain electrodes, which are subject to an ac voltage, focusing on signatures imprinted on the charge transport by the side-attached Majorana zero-energy mode. The considerations are based on the Kubo formula, for which the relevant correlation functions are determined by using the numerical renormalization group approach, which allows us to consider the correlation effects due to the Coulomb repulsion and their interplay with the Majorana mode in a nonperturbative manner. We point out universal features of the dynamical conductance, showing up in the Kondo-Majorana regime, and differentiate them against the conventional Kondo and Majorana systems. In particular, we predict that the Majorana quasiparticles give rise to universal fractional values of the ac conductance in the well-defined frequency range below the peak at the Kondo scale. We also show this Kondo scale to actually increase with strengthening the coupling to the topological superconducting wire.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We analyze dynamical transport properties of a hybrid nanostructure, comprising a correlated quantum dot embedded between the source and drain electrodes, which are subject to an ac voltage, focusing on signatures imprinted on the charge transport by the side-attached Majorana zero-energy mode. The considerations are based on the Kubo formula, for which the relevant correlation functions are determined by using the numerical renormalization group approach, which allows us to consider the correlation effects due to the Coulomb repulsion and their interplay with the Majorana mode in a nonperturbative manner. We point out universal features of the dynamical conductance, showing up in the Kondo-Majorana regime, and differentiate them against the conventional Kondo and Majorana systems. In particular, we predict that the Majorana quasiparticles give rise to universal fractional values of the ac conductance in the well-defined frequency range below the peak at the Kondo scale. We also show this Kondo scale to actually increase with strengthening the coupling to the topological superconducting wire. |
| 50. | Wojciech Rudziński, Józef Barnaś, Anna Dyrdał Spin waves in bilayers of transition metal dichalcogenides Physical Review B, 109 , pp. 035412, 2024. @article{Rudziński2024, title = {Spin waves in bilayers of transition metal dichalcogenides}, author = {Wojciech Rudziński and Józef Barnaś and Anna Dyrdał}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.109.035412}, doi = {10.1103/PhysRevB.109.035412}, year = {2024}, date = {2024-01-11}, journal = {Physical Review B}, volume = {109}, pages = {035412}, abstract = {Van der Waals magnetic materials are currently of great interest as materials for applications in future ultrathin nanoelectronics and nanospintronics. Due to weak coupling between individual monolayers, these materials can be easily obtained in the monolayer and bilayer forms. The latter are of specific interest as they may be considered as natural two-dimensional spin valves. In this paper, we theoretically study spin waves in bilayers of transition metal dichalcogenides. The considerations are carried within the general spin wave theory based on effective spin Hamiltonian and Holstein-Primakoff-Bogolubov transformation. The spin Hamiltonian includes intralayer as well as interlayer nearest-neighbor exchange interactions, easy-plane anisotropy, and additionally a weak in-plane easy-axis anisotropy. The bilayer systems consist of two ferromagnetic (in-plane magnetization) monolayers that are coupled either ferromagnetically or antiferromagnetically. In the latter case, we analyze the spin-wave spectra in all magnetic phases, i.e., in the antiferromagnetic, spin-flop, and ferromagnetic ones.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Van der Waals magnetic materials are currently of great interest as materials for applications in future ultrathin nanoelectronics and nanospintronics. Due to weak coupling between individual monolayers, these materials can be easily obtained in the monolayer and bilayer forms. The latter are of specific interest as they may be considered as natural two-dimensional spin valves. In this paper, we theoretically study spin waves in bilayers of transition metal dichalcogenides. The considerations are carried within the general spin wave theory based on effective spin Hamiltonian and Holstein-Primakoff-Bogolubov transformation. The spin Hamiltonian includes intralayer as well as interlayer nearest-neighbor exchange interactions, easy-plane anisotropy, and additionally a weak in-plane easy-axis anisotropy. The bilayer systems consist of two ferromagnetic (in-plane magnetization) monolayers that are coupled either ferromagnetically or antiferromagnetically. In the latter case, we analyze the spin-wave spectra in all magnetic phases, i.e., in the antiferromagnetic, spin-flop, and ferromagnetic ones. |
| 49. | Amir N. Zarezad, Józef Barnaś, Anna Dyrdał, Alireza Qaiumzadeh Skyrmion-deriven topological spin and charge Hall effects in diffusive antiferromagnetic thin films Journal of Magnetism and Magnetic Materials, 589 , pp. 171599, 2024. @article{Zarezad2024, title = {Skyrmion-deriven topological spin and charge Hall effects in diffusive antiferromagnetic thin films}, author = {Amir N. Zarezad and Józef Barnaś and Anna Dyrdał and Alireza Qaiumzadeh}, url = {https://www.sciencedirect.com/science/article/pii/S0304885323012490?via%3Dihub}, doi = {10.1016/j.jmmm.2023.171599}, year = {2024}, date = {2024-01-01}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {589}, pages = { 171599}, abstract = {We investigate topological Hall effects in a metallic antiferromagnetic (AFM) thin film and/or at the interface of an AFM insulator–normal metal bilayer with a single skyrmion in the diffusive regime. To determine the spin- and charge Hall currents, we employed a Boltzmann kinetic equation with both spin-dependent and spin-flip scatterings. The interaction between conduction electrons and static skyrmions is included in the Boltzmann equation via the corresponding emergent magnetic field arising from the skyrmion texture. We compute intrinsic and extrinsic contributions to the topological spin Hall effect and spin accumulation, induced by an AFM skyrmion. We show that although the spin Hall current vanishes rapidly outside the skyrmion, the spin accumulation can be finite at the edges far from the skyrmion, provided the spin diffusion length is longer than the skyrmion radius. In addition, We show that in the presence of a spin-dependent relaxation time, the topological charge Hall effect is finite and we determine the corresponding Hall voltage. Our results may help to explore antiferromagnetic skyrmions by electrical means in real materials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We investigate topological Hall effects in a metallic antiferromagnetic (AFM) thin film and/or at the interface of an AFM insulator–normal metal bilayer with a single skyrmion in the diffusive regime. To determine the spin- and charge Hall currents, we employed a Boltzmann kinetic equation with both spin-dependent and spin-flip scatterings. The interaction between conduction electrons and static skyrmions is included in the Boltzmann equation via the corresponding emergent magnetic field arising from the skyrmion texture. We compute intrinsic and extrinsic contributions to the topological spin Hall effect and spin accumulation, induced by an AFM skyrmion. We show that although the spin Hall current vanishes rapidly outside the skyrmion, the spin accumulation can be finite at the edges far from the skyrmion, provided the spin diffusion length is longer than the skyrmion radius. In addition, We show that in the presence of a spin-dependent relaxation time, the topological charge Hall effect is finite and we determine the corresponding Hall voltage. Our results may help to explore antiferromagnetic skyrmions by electrical means in real materials. |
| 48. | Anna Krzyżewska, Anna Dyrdał Bilinear magnetoresistance in 2DEG with isotropic cubic Rashba spin–orbit interaction Journal of Magnetism and Magnetic Materials, 589 , pp. 171615, 2024. @article{Krzyżewska2024, title = {Bilinear magnetoresistance in 2DEG with isotropic cubic Rashba spin–orbit interaction}, author = {Anna Krzyżewska and Anna Dyrdał}, url = {https://www.sciencedirect.com/science/article/pii/S0304885323012659?via%3Dihub}, doi = {10.1016/j.jmmm.2023.171615}, year = {2024}, date = {2024-01-01}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {589}, pages = {171615}, abstract = {Bilinear magnetoresistance has been studied theoretically in 2D systems with isotropic cubic form of Rashba spin–orbit interaction. We have derived the effective spin–orbital field due to current-induced spin polarization and discussed its contribution to the unidirectional system response. The analyzed model can be applied to the semiconductor quantum wells as well as 2DEG at the surfaces and interfaces of perovskite oxides.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Bilinear magnetoresistance has been studied theoretically in 2D systems with isotropic cubic form of Rashba spin–orbit interaction. We have derived the effective spin–orbital field due to current-induced spin polarization and discussed its contribution to the unidirectional system response. The analyzed model can be applied to the semiconductor quantum wells as well as 2DEG at the surfaces and interfaces of perovskite oxides. |
| 47. | Mirali Jafari, Anna Dyrdał Journal of Magnetism and Magnetic Materials, 589 , pp. 171618, 2024. @article{Jafari2024, title = {Effect of strain on the electronic and magnetic properties of bilayer T-phase VS2 : A first-principles study}, author = {Mirali Jafari and Anna Dyrdał}, url = {https://www.sciencedirect.com/science/article/pii/S0304885323012684?via%3Dihub}, doi = {10.1016/j.jmmm.2023.171618}, year = {2024}, date = {2024-01-01}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {589}, pages = {171618}, abstract = {Using the Density Functional Theory (DFT) calculations, we determined the electronic and magnetic properties of a T-phase VS2 bilayer as a function of tensile and compressive strain. First, we determine the ground state structural parameters and then the band structure, magnetic anisotropy, exchange parameters, and Curie temperature. Variation of these parameters with the strain is carefully analyzed and described. The easy-plane anisotropy, which is rather small in the absence of strain, becomes remarkably enhanced by tensile strain and reduced almost to zero by compressive strain. We also show that the exchange parameters and the Curie temperature are remarkably reduced for the compressive strains below roughly −4%. }, keywords = {}, pubstate = {published}, tppubtype = {article} } Using the Density Functional Theory (DFT) calculations, we determined the electronic and magnetic properties of a T-phase VS2 bilayer as a function of tensile and compressive strain. First, we determine the ground state structural parameters and then the band structure, magnetic anisotropy, exchange parameters, and Curie temperature. Variation of these parameters with the strain is carefully analyzed and described. The easy-plane anisotropy, which is rather small in the absence of strain, becomes remarkably enhanced by tensile strain and reduced almost to zero by compressive strain. We also show that the exchange parameters and the Curie temperature are remarkably reduced for the compressive strains below roughly −4%. |
| 46. | Emil Siuda, Piotr Trocha Thermal generation of spin current in a quantum dot coupled to magnetic insulators Journal of Magnetism and Magnetic Materials, 589 , pp. 171495, 2024. @article{Siuda2024, title = {Thermal generation of spin current in a quantum dot coupled to magnetic insulators}, author = {Emil Siuda and Piotr Trocha}, url = {https://www.sciencedirect.com/science/article/pii/S0304885323011459}, doi = {/10.1016/j.jmmm.2023.171495}, year = {2024}, date = {2024-01-01}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {589}, pages = {171495}, abstract = {In this work, we study thermally-generated spin current in the system consisting of a quantum dot connected to two magnetic insulators. The external leads are kept at different temperatures which leads to an imbalance of magnon populations in two magnetic insulators resulting in the flow of the magnon (spin) current. We take into account many-body magnon interactions and incorporate energy-dependent density of states of the magnetic insulators. Both features can strongly affect magnon distribution in the magnetic insulators and the coupling strengths between the leads and the dot, and thus, the thermally generated spin current. All the calculations are carried out in the weak coupling regime. We show, that results obtained with a density of states being a function of energy differ significantly from the ones obtained with a density of states taken as a constant. In turn, magnon interactions in the leads proved to be important at high temperatures and large values of energy of transported spin waves.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work, we study thermally-generated spin current in the system consisting of a quantum dot connected to two magnetic insulators. The external leads are kept at different temperatures which leads to an imbalance of magnon populations in two magnetic insulators resulting in the flow of the magnon (spin) current. We take into account many-body magnon interactions and incorporate energy-dependent density of states of the magnetic insulators. Both features can strongly affect magnon distribution in the magnetic insulators and the coupling strengths between the leads and the dot, and thus, the thermally generated spin current. All the calculations are carried out in the weak coupling regime. We show, that results obtained with a density of states being a function of energy differ significantly from the ones obtained with a density of states taken as a constant. In turn, magnon interactions in the leads proved to be important at high temperatures and large values of energy of transported spin waves. |
2023 |
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| 45. | Wojciech Rudziński, Józef Barnaś, Anna Dyrdał Journal of Magnetism and Magnetic Materials, 588 , pp. 171463, 2023. @article{Rudzinski2023, title = {Spin waves in monolayers of transition-metal dichalcogenides with Dzyaloshinskii - Moriya interaction}, author = {Wojciech Rudziński and Józef Barnaś and Anna Dyrdał}, url = {https://doi.org/10.1016/j.jmmm.2023.171463}, doi = {10.1016/j.jmmm.2023.171463}, year = {2023}, date = {2023-12-15}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {588}, pages = {171463}, abstract = {Dzyaloshinski–Moriya interaction, known also as the antisymmetric exchange coupling, leads to a variety of interesting spin phenomena, like spin canting, skyrmion formation, nonreciprocal spin wave propagation, and others. In this paper we analyze spin waves in monolayers of two-dimensional van–der–Waals materials, such as Vanadium–based dichalcogenides, VX2 (X=S, Se, Te) and other materials of similar symmetry. The considerations are limited to a collinear spin ground state, stabilized by a sufficiently strong magnetic anisotropy. The theoretical analysis is performed within the general spin wave theory based on the Holstein–Primakoff–Bogoliubov transformation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Dzyaloshinski–Moriya interaction, known also as the antisymmetric exchange coupling, leads to a variety of interesting spin phenomena, like spin canting, skyrmion formation, nonreciprocal spin wave propagation, and others. In this paper we analyze spin waves in monolayers of two-dimensional van–der–Waals materials, such as Vanadium–based dichalcogenides, VX2 (X=S, Se, Te) and other materials of similar symmetry. The considerations are limited to a collinear spin ground state, stabilized by a sufficiently strong magnetic anisotropy. The theoretical analysis is performed within the general spin wave theory based on the Holstein–Primakoff–Bogoliubov transformation. |
| 44. | Anand Manaparambil, Ireneusz Weymann Giant tunnel magnetoresistance induced by thermal bias Journal of Magnetism and Magnetic Materials, 587 , pp. 171272, 2023. @article{Manaparambil2023b, title = {Giant tunnel magnetoresistance induced by thermal bias}, author = {Anand Manaparambil and Ireneusz Weymann}, url = {https://www.sciencedirect.com/science/article/pii/S0304885323009228}, doi = {10.1016/j.jmmm.2023.171272}, year = {2023}, date = {2023-12-01}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {587}, pages = {171272}, abstract = {We analyze the spin-resolved transport and, in particular, the tunnel magnetoresistance of an asymmetric ferromagnetic tunnel junction with an embedded quantum dot or molecule subject to thermal and voltage bias in the nonlinear response regime. We demonstrate that such system exhibits a giant tunnel magnetoresistance effect that can be tuned by gate and bias voltages. Large values of magnetoresistance are associated with the interplay between the Kondo correlations and the ferromagnetic-contact-induced exchange field. In particular, we show that the nonequilibrium current in the parallel and antiparallel magnetic configuration of the system changes sign at different values of the voltage and thermal bias. This gives rise to giant values of magnetoresistance, the sign of which can be controlled by the applied sources.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We analyze the spin-resolved transport and, in particular, the tunnel magnetoresistance of an asymmetric ferromagnetic tunnel junction with an embedded quantum dot or molecule subject to thermal and voltage bias in the nonlinear response regime. We demonstrate that such system exhibits a giant tunnel magnetoresistance effect that can be tuned by gate and bias voltages. Large values of magnetoresistance are associated with the interplay between the Kondo correlations and the ferromagnetic-contact-induced exchange field. In particular, we show that the nonequilibrium current in the parallel and antiparallel magnetic configuration of the system changes sign at different values of the voltage and thermal bias. This gives rise to giant values of magnetoresistance, the sign of which can be controlled by the applied sources. |
| 43. | Mirali Jafari, Wojciech Rudziński, Józef Barnaś, Anna Dyrdał Electronic and magnetic properties of 2D vanadium-based transition metal dichalcogenides Scientific Reports, 13 , pp. 20947, 2023. @article{Jafari2023, title = {Electronic and magnetic properties of 2D vanadium-based transition metal dichalcogenides}, author = {Mirali Jafari and Wojciech Rudziński and Józef Barnaś and Anna Dyrdał}, url = {https://doi.org/10.1038/s41598-023-48141-1}, doi = {10.1038/s41598-023-48141-1}, year = {2023}, date = {2023-11-28}, journal = {Scientific Reports}, volume = {13}, pages = {20947}, abstract = {In this paper, electronic and magnetic properties of monolayers and bilayers of Vanadium-based transition metal dichalcogenides VX2 (X = S, Se, Te) in the H phase are investigated theoretically using methods based on DFT calculations as well as analytical methods based on effective spin Hamiltonians. The band structure has been computed for all systems, and then the results have been used to determine exchange parameters and magnetic anisotropy constants. These parameters are subsequently used for the determination of the Curie temperatures, hysteresis curves, and energy of spin-wave excitations. In the latter case, we compare analytical results based on effective spin Hamiltonian with those determined numerically by Quantum ATK software and find a good agreement. The determined Curie temperature for VTe2 monolayers and bilayers is below the room temperature (especially that for bilayers), while for the other two materials, i.e. for VS2 and VSe2, it is above the room temperature, in agreement with available experimental data.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, electronic and magnetic properties of monolayers and bilayers of Vanadium-based transition metal dichalcogenides VX2 (X = S, Se, Te) in the H phase are investigated theoretically using methods based on DFT calculations as well as analytical methods based on effective spin Hamiltonians. The band structure has been computed for all systems, and then the results have been used to determine exchange parameters and magnetic anisotropy constants. These parameters are subsequently used for the determination of the Curie temperatures, hysteresis curves, and energy of spin-wave excitations. In the latter case, we compare analytical results based on effective spin Hamiltonian with those determined numerically by Quantum ATK software and find a good agreement. The determined Curie temperature for VTe2 monolayers and bilayers is below the room temperature (especially that for bilayers), while for the other two materials, i.e. for VS2 and VSe2, it is above the room temperature, in agreement with available experimental data. |
| 42. | Kacper Wrześniewski, Tomasz Ślusarski, Ireneusz Weymann Nonmonotonic buildup of spin-singlet correlations in a double quantum dot Physical Review B, 108 , pp. 144307, 2023. @article{Wrześniewski2023b, title = {Nonmonotonic buildup of spin-singlet correlations in a double quantum dot}, author = {Kacper Wrześniewski and Tomasz Ślusarski and Ireneusz Weymann}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.108.144307}, doi = {10.1103/PhysRevB.108.144307}, year = {2023}, date = {2023-10-27}, journal = {Physical Review B}, volume = {108}, pages = {144307}, abstract = {Dynamical buildup of spin-singlet correlations between the two quantum dots is investigated by means of the time-dependent numerical renormalization group method. By calculating the time evolution of the spin-spin expectation value upon a quench in the hopping between the quantum dots, we examine the timescales associated with the development of an entangled spin-singlet state in the system. Interestingly, we predict a nonmonotonic buildup of entanglement between the two dots. In particular, we find that in short timescales the effective exchange interaction between the quantum dots is of ferromagnetic type, favoring spin-triplet correlations, as opposed to the long-time limit, when strong antiferromagnetic correlations develop and eventually an entangled spin-singlet state is formed between the dots. We also numerically determine the relevant timescales and show that the physics is generally governed by the interplay between the Kondo correlations on each dot and exchange interaction between the spins of both quantum dots.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Dynamical buildup of spin-singlet correlations between the two quantum dots is investigated by means of the time-dependent numerical renormalization group method. By calculating the time evolution of the spin-spin expectation value upon a quench in the hopping between the quantum dots, we examine the timescales associated with the development of an entangled spin-singlet state in the system. Interestingly, we predict a nonmonotonic buildup of entanglement between the two dots. In particular, we find that in short timescales the effective exchange interaction between the quantum dots is of ferromagnetic type, favoring spin-triplet correlations, as opposed to the long-time limit, when strong antiferromagnetic correlations develop and eventually an entangled spin-singlet state is formed between the dots. We also numerically determine the relevant timescales and show that the physics is generally governed by the interplay between the Kondo correlations on each dot and exchange interaction between the spins of both quantum dots. |
| 41. | Alexandre Huguet, Kacper Wrześniewski, Ireneusz Weymann Spin effects on transport and zero-bias anomaly in a hybrid Majorana wire-quantum dot system Scientific Reports, 13 , pp. 17279, 2023, ISSN: 2045-2322. @article{Huguet2023, title = {Spin effects on transport and zero-bias anomaly in a hybrid Majorana wire-quantum dot system}, author = {Alexandre Huguet and Kacper Wrześniewski and Ireneusz Weymann }, url = {https://www.nature.com/articles/s41598-023-44254-9}, doi = {10.1038/s41598-023-44254-9}, issn = {2045-2322}, year = {2023}, date = {2023-10-12}, journal = {Scientific Reports}, volume = {13}, pages = {17279}, abstract = {We examine the impact of spin effects on the nonequilibrium transport properties of a nanowire hosting Majorana zero-energy modes at its ends, coupled to a quantum dot junction with ferromagnetic leads. Using the real-time diagrammatic technique, we determine the current, differential conductance and current cross-correlations in the nonlinear response regime. We also explore transport in different magnetic configurations of the system, which can be quantified by the tunnel magnetoresistance. We show that the presence of Majorana quasiparticles gives rise to unique features in all spin-resolved transport characteristics, in particular, to zero-bias anomaly, negative differential conductance, negative tunnel magnetoresistance, and it is also reflected in the current cross-correlations. Moreover, we study the dependence of the zero-bias anomaly on various system parameters and demonstrate its dependence on the magnetic configuration of the system as well as on the degree of spin polarization in the leads. A highly nontrivial behavior is also found for the tunnel magnetoresistance, which exhibits regions of enhanced or negative values—new features resulting from the coupling to Majorana wire.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We examine the impact of spin effects on the nonequilibrium transport properties of a nanowire hosting Majorana zero-energy modes at its ends, coupled to a quantum dot junction with ferromagnetic leads. Using the real-time diagrammatic technique, we determine the current, differential conductance and current cross-correlations in the nonlinear response regime. We also explore transport in different magnetic configurations of the system, which can be quantified by the tunnel magnetoresistance. We show that the presence of Majorana quasiparticles gives rise to unique features in all spin-resolved transport characteristics, in particular, to zero-bias anomaly, negative differential conductance, negative tunnel magnetoresistance, and it is also reflected in the current cross-correlations. Moreover, we study the dependence of the zero-bias anomaly on various system parameters and demonstrate its dependence on the magnetic configuration of the system as well as on the degree of spin polarization in the leads. A highly nontrivial behavior is also found for the tunnel magnetoresistance, which exhibits regions of enhanced or negative values—new features resulting from the coupling to Majorana wire. |
| 40. | Anna Dyrdał, Alireza Qaiumzadeh, Arne Brataas, Józef Barnaś Magnon-plasmon hybridization mediated by spin-orbit interaction in magnetic materials Physical Review B, 108 (4), pp. 045414, 2023. @article{Dyrdał2023, title = {Magnon-plasmon hybridization mediated by spin-orbit interaction in magnetic materials}, author = {Anna Dyrdał and Alireza Qaiumzadeh and Arne Brataas and Józef Barnaś}, url = {https://doi.org/10.1103/PhysRevB.108.045414}, doi = {10.1103/PhysRevB.108.045414}, year = {2023}, date = {2023-07-21}, journal = {Physical Review B}, volume = {108}, number = {4}, pages = {045414}, abstract = {We propose a mechanism for magnon-plasmon coupling and hybridization in ferromagnetic (FM) and antiferromagnetic (AFM) systems. The electric field associated with plasmon oscillations creates a nonequilibrium spin density via the inverse spin galvanic effect. This plasmon-induced spin density couples to magnons by an exchange interaction. The strength of magnon-plasmon coupling depends on the magnetoelectric susceptibility of the system and the wavevector at which the level repulsion has happened. This wavevector may be tuned by an applied magnetic field. In AFM systems, the degeneracy of two chiral magnons is broken in the presence of a magnetic field, and we find two separate hybrid modes for left-handed and right-handed AFM magnons. Furthermore, we show that magnon-plasmon coupling in AFM systems is enhanced because of strong intrasublattice spin dynamics. We argue that the recently discovered two-dimensional magnetic systems are ideal platforms to investigate proposed magnon-plasmon hybrid modes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We propose a mechanism for magnon-plasmon coupling and hybridization in ferromagnetic (FM) and antiferromagnetic (AFM) systems. The electric field associated with plasmon oscillations creates a nonequilibrium spin density via the inverse spin galvanic effect. This plasmon-induced spin density couples to magnons by an exchange interaction. The strength of magnon-plasmon coupling depends on the magnetoelectric susceptibility of the system and the wavevector at which the level repulsion has happened. This wavevector may be tuned by an applied magnetic field. In AFM systems, the degeneracy of two chiral magnons is broken in the presence of a magnetic field, and we find two separate hybrid modes for left-handed and right-handed AFM magnons. Furthermore, we show that magnon-plasmon coupling in AFM systems is enhanced because of strong intrasublattice spin dynamics. We argue that the recently discovered two-dimensional magnetic systems are ideal platforms to investigate proposed magnon-plasmon hybrid modes. |
| 39. | Ali Ebrahimian, Anna Dyrdał, Alireza Qaiumzadeh Scientific Reports, 13 , pp. 5336, 2023. @article{Ebrahimian2023, title = {Control of magnetic states and spin interactions in bilayer CrCl3 with strain and electric fields: an ab initio study}, author = {Ali Ebrahimian and Anna Dyrdał and Alireza Qaiumzadeh}, url = {https://doi.org/10.1038/s41598-023-32598-1}, doi = {10.1038/s41598-023-32598-1}, year = {2023}, date = {2023-04-01}, journal = {Scientific Reports}, volume = {13}, pages = {5336}, abstract = {Using ab initio density functional theory, we demonstrated the possibility of controlling the magnetic ground-state properties of bilayer CrCl3 by means of mechanical strains and electric fields. In principle, we investigated the influence of these two fields on parameters describing the spin Hamiltonian of the system. The obtained results show that biaxial strains change the magnetic ground state between ferromagnetic and antiferromagnetic phases. The mechanical strain also affects the direction and amplitude of the magnetic anisotropy energy (MAE). Importantly, the direction and amplitude of the Dzyaloshinskii–Moriya vectors are also highly tunable under external strain and electric fields. The competition between nearest-neighbor exchange interactions, MAE, and Dzyaloshinskii–Moriya interactions can lead to the stabilization of various exotic spin textures and novel magnetic excitations. The high tunability of magnetic properties by external fields makes bilayer CrCl3 a promising candidate for application in the emerging field of two-dimensional quantum spintronics and magnonics.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Using ab initio density functional theory, we demonstrated the possibility of controlling the magnetic ground-state properties of bilayer CrCl3 by means of mechanical strains and electric fields. In principle, we investigated the influence of these two fields on parameters describing the spin Hamiltonian of the system. The obtained results show that biaxial strains change the magnetic ground state between ferromagnetic and antiferromagnetic phases. The mechanical strain also affects the direction and amplitude of the magnetic anisotropy energy (MAE). Importantly, the direction and amplitude of the Dzyaloshinskii–Moriya vectors are also highly tunable under external strain and electric fields. The competition between nearest-neighbor exchange interactions, MAE, and Dzyaloshinskii–Moriya interactions can lead to the stabilization of various exotic spin textures and novel magnetic excitations. The high tunability of magnetic properties by external fields makes bilayer CrCl3 a promising candidate for application in the emerging field of two-dimensional quantum spintronics and magnonics. |
| 38. | Kacper Wrześniewski Dynamics of Superconducting Correlations Induced by Hopping in Serial Double Quantum Dot System Acta Physica Polonica A, 143 (2), pp. 160, 2023. @article{Wrześniewski2023, title = {Dynamics of Superconducting Correlations Induced by Hopping in Serial Double Quantum Dot System}, author = {Kacper Wrześniewski}, url = {http://przyrbwn.icm.edu.pl/APP/apphome.html}, doi = {10.12693/APhysPolA.143.160}, year = {2023}, date = {2023-02-27}, journal = {Acta Physica Polonica A}, volume = {143}, number = {2}, pages = {160}, abstract = {We study the quench dynamics of superconducting pairing correlations in the double quantum dotsystem coupled to superconducting and normal metallic electrodes. The quantum dots are initiallyisolated from each other, and the subsequent dynamics are induced by the sudden switching on hoppingbetween them. We focus on the time-dependence of the real and imaginary parts of dots pairing potentialand the role of the hopping amplitude and on-site Coulomb correlations. For relatively small hoppingvalues, the evolution of the pairing potential is suppressed due to a strong single-occupation blockade.As the hopping amplitude increases, the pairing potential is dynamically redistributed between thedots and can eventually assume values of opposite signs. This effect is enhanced by the presence ofstrong on-site Coulomb interactions. The discussed numerical results are obtained by means of thetime-dependent numerical renormalization group approach.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We study the quench dynamics of superconducting pairing correlations in the double quantum dotsystem coupled to superconducting and normal metallic electrodes. The quantum dots are initiallyisolated from each other, and the subsequent dynamics are induced by the sudden switching on hoppingbetween them. We focus on the time-dependence of the real and imaginary parts of dots pairing potentialand the role of the hopping amplitude and on-site Coulomb correlations. For relatively small hoppingvalues, the evolution of the pairing potential is suppressed due to a strong single-occupation blockade.As the hopping amplitude increases, the pairing potential is dynamically redistributed between thedots and can eventually assume values of opposite signs. This effect is enhanced by the presence ofstrong on-site Coulomb interactions. The discussed numerical results are obtained by means of thetime-dependent numerical renormalization group approach. |
| 37. | Krzysztof Paweł Wójcik, Piotr Majek Majorana Coupling and Kondo Screening of Localized Spins Acta Physica Polonica A, 143 (2), pp. 207, 2023. @article{Wójcik2023, title = {Majorana Coupling and Kondo Screening of Localized Spins}, author = {Krzysztof Paweł Wójcik and Piotr Majek}, url = {http://przyrbwn.icm.edu.pl/APP/PDF/143/app143z2p15.pdf}, doi = {10.12693/APhysPolA.143.207}, year = {2023}, date = {2023-02-27}, journal = {Acta Physica Polonica A}, volume = {143}, number = {2}, pages = {207}, abstract = {We perform a theoretical analysis of the fate of the local magnetic moment of a quantum dot coupled to a normal metallic lead and a topological superconducting wire hosting Majorana modes at the ends. By means of simple analytical tools and numerical renormalization group calculations, we show that the proximity of the Majorana mode reduces the magnetic moment from 1/4, characteristic of a free spin 1/2, to 1/16. Coupling to the normal lead then causes the Kondo effect, such that the magnetic moment is fully screened below the Kondo temperature. The latter is vastly increased for strong coupling to Majorana mode.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We perform a theoretical analysis of the fate of the local magnetic moment of a quantum dot coupled to a normal metallic lead and a topological superconducting wire hosting Majorana modes at the ends. By means of simple analytical tools and numerical renormalization group calculations, we show that the proximity of the Majorana mode reduces the magnetic moment from 1/4, characteristic of a free spin 1/2, to 1/16. Coupling to the normal lead then causes the Kondo effect, such that the magnetic moment is fully screened below the Kondo temperature. The latter is vastly increased for strong coupling to Majorana mode. |
| 36. | Anand Manaparambil, Ireneusz Weymann Nonequilibrium Seebeck effect and thermoelectric efficiency of Kondo-correlated molecular junctions Phys. Rev. B, 107 , pp. 085404, 2023. @article{Manaparambil2023, title = {Nonequilibrium Seebeck effect and thermoelectric efficiency of Kondo-correlated molecular junctions}, author = {Anand Manaparambil and Ireneusz Weymann}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.107.085404}, doi = {10.1103/PhysRevB.107.085404}, year = {2023}, date = {2023-02-07}, journal = {Phys. Rev. B}, volume = {107}, pages = {085404}, abstract = {We theoretically study the nonequilibrium thermoelectric transport properties of a strongly-correlated molecule (or quantum dot) embedded in a tunnel junction. Assuming that the coupling of the molecule to the contacts is asymmetric, we determine the nonlinear current driven by the voltage and temperature gradients by using the perturbation theory. However, the subsystem consisting of the molecule strongly coupled to one of the contacts is solved by using the numerical renormalization group method, which allows for accurate description of Kondo correlations. We study the temperature gradient and voltage dependence of the nonlinear and differential Seebeck coefficients for various initial configurations of the system. In particular, we show that in the Coulomb blockade regime with singly occupied molecule, both thermopowers exhibit sign changes due to the Kondo correlations at nonequilibrium conditions. Moreover, we determine the nonlinear heat current and thermoelectric efficiency, demonstrating that the system can work as a heat engine with considerable efficiency, depending on the transport regime.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We theoretically study the nonequilibrium thermoelectric transport properties of a strongly-correlated molecule (or quantum dot) embedded in a tunnel junction. Assuming that the coupling of the molecule to the contacts is asymmetric, we determine the nonlinear current driven by the voltage and temperature gradients by using the perturbation theory. However, the subsystem consisting of the molecule strongly coupled to one of the contacts is solved by using the numerical renormalization group method, which allows for accurate description of Kondo correlations. We study the temperature gradient and voltage dependence of the nonlinear and differential Seebeck coefficients for various initial configurations of the system. In particular, we show that in the Coulomb blockade regime with singly occupied molecule, both thermopowers exhibit sign changes due to the Kondo correlations at nonequilibrium conditions. Moreover, we determine the nonlinear heat current and thermoelectric efficiency, demonstrating that the system can work as a heat engine with considerable efficiency, depending on the transport regime. |
2022 |
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| 35. | Irina Werner, Jan Griebel, Albert Masip-Sánchez, Xavier López, Karol Załęski, Piotr Kozłowski, Axel Kahnt, Martin Boerner, Ziyan Warneke, Jonas Warneke, Kirill Yu. Monakhov Inorganic Chemistry, 62 (9), pp. 3761-3775, 2022, (PMID: 36534941). @article{doi:10.1021/acs.inorgchem.2c03599, title = {Hybrid Molecular Magnets with Lanthanide- and Countercation-Mediated Interfacial Electron Transfer between Phthalocyanine and Polyoxovanadate}, author = {Irina Werner and Jan Griebel and Albert Masip-Sánchez and Xavier López and Karol Załęski and Piotr Kozłowski and Axel Kahnt and Martin Boerner and Ziyan Warneke and Jonas Warneke and Kirill Yu. Monakhov}, url = {https://doi.org/10.1021/acs.inorgchem.2c03599}, doi = {10.1021/acs.inorgchem.2c03599}, year = {2022}, date = {2022-12-19}, journal = {Inorganic Chemistry}, volume = {62}, number = {9}, pages = {3761-3775}, note = {PMID: 36534941}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 34. | Piotr Majek, Grzegorz Górski, Tadeusz Domański, Ireneusz Weymann Hallmarks of Majorana mode leaking into a hybrid double quantum dot Phys. Rev. B, 106 , pp. 155123, 2022. @article{Majek2022c, title = {Hallmarks of Majorana mode leaking into a hybrid double quantum dot}, author = {Piotr Majek and Grzegorz Górski and Tadeusz Domański and Ireneusz Weymann}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.106.155123}, doi = {10.1103/PhysRevB.106.155123}, year = {2022}, date = {2022-10-13}, journal = {Phys. Rev. B}, volume = {106}, pages = {155123}, abstract = {We investigate the spectral and transport properties of a double quantum dot laterally attached to a topological superconducting nanowire, hosting the Majorana zero-energy modes. Specifically, we consider a geometry, in which the outer quantum dot is embedded between the external normal and superconducting leads, forming a circuit. First, we derive analytical expressions for the bound states in the case of an uncorrelated system and discuss their signatures in the tunneling spectroscopy. Then, we explore the case of strongly correlated quantum dots by performing the numerical renormalization group calculations, focusing on the interplay and relationship between the leaking Majorana mode and the Kondo states on both quantum dots. Finally, we discuss feasible means to experimentally probe the in-gap quasiparticles by using the Andreev spectroscopy based on the particle-to-hole scattering mechanism.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We investigate the spectral and transport properties of a double quantum dot laterally attached to a topological superconducting nanowire, hosting the Majorana zero-energy modes. Specifically, we consider a geometry, in which the outer quantum dot is embedded between the external normal and superconducting leads, forming a circuit. First, we derive analytical expressions for the bound states in the case of an uncorrelated system and discuss their signatures in the tunneling spectroscopy. Then, we explore the case of strongly correlated quantum dots by performing the numerical renormalization group calculations, focusing on the interplay and relationship between the leaking Majorana mode and the Kondo states on both quantum dots. Finally, we discuss feasible means to experimentally probe the in-gap quasiparticles by using the Andreev spectroscopy based on the particle-to-hole scattering mechanism. |
| 33. | X.-G. Wang, L. Chotorlishvili, G. Tatara, Anna Dyrdał, Guang-hua Guo, V. K. Dugaev, Józef Barnaś, S.S.P. Parkin, A. Ernst Skyrmion lattice hosted in synthetic antiferromagnets and helix modes Phys. Rev. B, 106 , pp. 104424, 2022. @article{Wang2022b, title = {Skyrmion lattice hosted in synthetic antiferromagnets and helix modes}, author = {X.-G. Wang and L. Chotorlishvili and G. Tatara and Anna Dyrdał and Guang-hua Guo and V. K. Dugaev and Józef Barnaś and S.S.P. Parkin and A. Ernst}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.106.104424}, doi = {10.1103/PhysRevB.106.104424}, year = {2022}, date = {2022-09-20}, journal = {Phys. Rev. B}, volume = {106}, pages = {104424}, abstract = {Thin ferromagnetic films can possess unconventional magnetic properties, opening a new road for using them in spintronic technologies. In the present work exploiting three different methods, we comprehensively analyze phason excitations of a skyrmion lattice in synthetic antiferromagnets. To analyze phason excitations of the skyrmion lattice, we have constructed an analytical model based on three coupled helices and found a linear gapless mode. Micromagnetic simulations also support this result. Moreover, a similar result has been achieved within the rigid skyrmion lattice model based on the coupled Thiele's equations, when the coupling between skyrmions in different layers of the synthetic antiferromagnetic is comparable to or larger than the intralayer coupling. In addition, we also consider the orbital angular momentum and spin pumping current associated with phason excitations. Due to the gapless excitations in the case of skyrmion lattice, the pumping current is nonzero for the arbitrary frequency of pumping microwaves. In the case of individual skyrmions, no current is pumped when microwave frequency is inside the gap of the spectrum of individual skyrmions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Thin ferromagnetic films can possess unconventional magnetic properties, opening a new road for using them in spintronic technologies. In the present work exploiting three different methods, we comprehensively analyze phason excitations of a skyrmion lattice in synthetic antiferromagnets. To analyze phason excitations of the skyrmion lattice, we have constructed an analytical model based on three coupled helices and found a linear gapless mode. Micromagnetic simulations also support this result. Moreover, a similar result has been achieved within the rigid skyrmion lattice model based on the coupled Thiele's equations, when the coupling between skyrmions in different layers of the synthetic antiferromagnetic is comparable to or larger than the intralayer coupling. In addition, we also consider the orbital angular momentum and spin pumping current associated with phason excitations. Due to the gapless excitations in the case of skyrmion lattice, the pumping current is nonzero for the arbitrary frequency of pumping microwaves. In the case of individual skyrmions, no current is pumped when microwave frequency is inside the gap of the spectrum of individual skyrmions. |
| 32. | X.-G. Wang, Guang-hua Guo, Anna Dyrdał, Józef Barnaś, V. K. Dugaev, S. S. P. Parkin, A. Ernst, L. Chotorlishvili Skyrmion Echo in a System of Interacting Skyrmions Phys. Rev. Lett., 129 , pp. 126101, 2022. @article{Wang2022, title = {Skyrmion Echo in a System of Interacting Skyrmions}, author = {X.-G. Wang and Guang-hua Guo and Anna Dyrdał and Józef Barnaś and V. K. Dugaev and S. S. P. Parkin and A. Ernst and L. Chotorlishvili}, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.126101}, doi = {10.1103/PhysRevLett.129.126101}, year = {2022}, date = {2022-09-14}, journal = {Phys. Rev. Lett.}, volume = {129}, pages = {126101}, abstract = {We consider helical rotation of skyrmions confined in the potentials formed by nanodisks. Based on numerical and analytical calculations we propose the skyrmion echo phenomenon. The physical mechanism of the skyrmion echo formation is also proposed. Because of the distortion of the lattice, impurities, or pinning effect, confined skyrmions experience slightly different local fields, which leads to dephasing of the initial signal. The interaction between skyrmions also can contribute to the dephasing process. However, switching the magnetization direction in the nanodiscs (e.g., by spin transfer torque) also switches the helical rotation of the skyrmions from clockwise to anticlockwise (or vice versa), and this restores the initial signal (which is the essence of skyrmion echo).}, keywords = {}, pubstate = {published}, tppubtype = {article} } We consider helical rotation of skyrmions confined in the potentials formed by nanodisks. Based on numerical and analytical calculations we propose the skyrmion echo phenomenon. The physical mechanism of the skyrmion echo formation is also proposed. Because of the distortion of the lattice, impurities, or pinning effect, confined skyrmions experience slightly different local fields, which leads to dephasing of the initial signal. The interaction between skyrmions also can contribute to the dephasing process. However, switching the magnetization direction in the nanodiscs (e.g., by spin transfer torque) also switches the helical rotation of the skyrmions from clockwise to anticlockwise (or vice versa), and this restores the initial signal (which is the essence of skyrmion echo). |
| 31. | Anand Manaparambil, Andreas Weichselbaum, Jan von Delft, Ireneusz Weymann Nonequilibrium spintronic transport through Kondo impurities Phys. Rev. B, 106 , pp. 125413, 2022. @article{Manaparambil2022, title = {Nonequilibrium spintronic transport through Kondo impurities}, author = {Anand Manaparambil and Andreas Weichselbaum and Jan von Delft and Ireneusz Weymann}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.106.125413}, doi = {10.1103/PhysRevB.106.125413}, year = {2022}, date = {2022-09-14}, journal = {Phys. Rev. B}, volume = {106}, pages = {125413}, abstract = {In this work we analyze the nonequilibrium transport through a quantum impurity (quantum dot or molecule) attached to ferromagnetic leads by using a hybrid numerical renormalization group–time-dependent density matrix renormalization group thermofield quench approach. For this, we study the bias dependence of the differential conductance through the system, which shows a finite zero-bias peak, characteristic of the Kondo resonance and reminiscent of the equilibrium local density of states. In the nonequilibrium settings, the resonance in the differential conductance is also found to decrease with increasing the lead spin polarization. The latter induces an effective exchange field that lifts the spin degeneracy of the dot level. Therefore, as we demonstrate, the Kondo resonance can be restored by counteracting the exchange field with a finite external magnetic field applied to the system. Finally, we investigate the influence of temperature on the nonequilibrium conductance, focusing on the split Kondo resonance. Our work thus provides an accurate quantitative description of the spin-resolved transport properties relevant for quantum dots and molecules embedded in magnetic tunnel junctions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work we analyze the nonequilibrium transport through a quantum impurity (quantum dot or molecule) attached to ferromagnetic leads by using a hybrid numerical renormalization group–time-dependent density matrix renormalization group thermofield quench approach. For this, we study the bias dependence of the differential conductance through the system, which shows a finite zero-bias peak, characteristic of the Kondo resonance and reminiscent of the equilibrium local density of states. In the nonequilibrium settings, the resonance in the differential conductance is also found to decrease with increasing the lead spin polarization. The latter induces an effective exchange field that lifts the spin degeneracy of the dot level. Therefore, as we demonstrate, the Kondo resonance can be restored by counteracting the exchange field with a finite external magnetic field applied to the system. Finally, we investigate the influence of temperature on the nonequilibrium conductance, focusing on the split Kondo resonance. Our work thus provides an accurate quantitative description of the spin-resolved transport properties relevant for quantum dots and molecules embedded in magnetic tunnel junctions. |
| 30. | L. Chotorlishvili, Xi-guang Wang, Anna Dyrdał, Guang-hua Guo, Vitalii K. Dugaev, Józef Barnaś, J. Berakdar Rectification of the spin Seebeck current in noncollinear antiferromagnets Phys. Rev. B, 106 (1), pp. 014417, 2022, ISSN: 2469-9969. @article{Chotorlishvili2022, title = {Rectification of the spin Seebeck current in noncollinear antiferromagnets}, author = {L. Chotorlishvili and Xi-guang Wang and Anna Dyrdał and Guang-hua Guo and Vitalii K. Dugaev and Józef Barnaś and J. Berakdar}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.106.014417}, doi = {10.1103/PhysRevB.106.014417}, issn = {2469-9969}, year = {2022}, date = {2022-07-25}, journal = {Phys. Rev. B}, volume = {106}, number = {1}, pages = {014417}, abstract = {In the absence of an external magnetic field and a spin-polarized charge current, an antiferromagnetic system supports two degenerate magnon modes. An applied thermal bias activates the magnetic dynamics, leading to a magnon flow from the hot to the cold edge (magnonic spin Seebeck current). Both degenerate bands contribute to the magnon current but the orientations of the magnetic moments underlying the magnons are opposite in different bands. Therefore, while the magnon current is nonzero, the net spin current is zero. To obtain a nonzero net spin current, one needs to apply either a magnetic field or a spin-polarized charge current that lifts the bands' degeneracy. Here, attaching a thermal contact to one edge of a helical nanowire, we study three different magnonic spin currents: (i) the exchange, and (ii) Dzyaloshinskii–Moriya spin currents flowing along the helical nanowire, and (iii) magnonic spin current pumped into the adjacent normal-metal layer. We find that the combination of Dzyaloshinskii–Moriya interaction and external magnetic field substantially enhances the spin current compared to the current generated solely through a magnetic field. Due to nonreciprocal magnons and magnon dichroism effect, the Dzyaloshinskii–Moriya and exchange spin currents show left-right propagation asymmetry, with 20% of current rectification. The spin pumping current shows a slight asymmetry only in the case of a strong Dzyaloshinskii–Moriya interaction. The observed effects are explained in terms of the magnon dispersion relations and the magnon Doppler effect.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In the absence of an external magnetic field and a spin-polarized charge current, an antiferromagnetic system supports two degenerate magnon modes. An applied thermal bias activates the magnetic dynamics, leading to a magnon flow from the hot to the cold edge (magnonic spin Seebeck current). Both degenerate bands contribute to the magnon current but the orientations of the magnetic moments underlying the magnons are opposite in different bands. Therefore, while the magnon current is nonzero, the net spin current is zero. To obtain a nonzero net spin current, one needs to apply either a magnetic field or a spin-polarized charge current that lifts the bands' degeneracy. Here, attaching a thermal contact to one edge of a helical nanowire, we study three different magnonic spin currents: (i) the exchange, and (ii) Dzyaloshinskii–Moriya spin currents flowing along the helical nanowire, and (iii) magnonic spin current pumped into the adjacent normal-metal layer. We find that the combination of Dzyaloshinskii–Moriya interaction and external magnetic field substantially enhances the spin current compared to the current generated solely through a magnetic field. Due to nonreciprocal magnons and magnon dichroism effect, the Dzyaloshinskii–Moriya and exchange spin currents show left-right propagation asymmetry, with 20% of current rectification. The spin pumping current shows a slight asymmetry only in the case of a strong Dzyaloshinskii–Moriya interaction. The observed effects are explained in terms of the magnon dispersion relations and the magnon Doppler effect. |
| 29. | Mir Ali Jafari, A. A. Kordbacheh, Anna Dyrdał J. Magn. Magn. Mater., 554 , pp. 169260, 2022, ISSN: 0304-8853. @article{Jafari2022b, title = {Electronic and magnetic properties of silicene monolayer under bi-axial mechanical strain: First principles study}, author = {Mir Ali Jafari and A. A. Kordbacheh and Anna Dyrdał}, url = {https://www.sciencedirect.com/science/article/pii/S0304885322002116?via%3Dihub}, doi = {10.1016/j.jmmm.2022.169260}, issn = {0304-8853}, year = {2022}, date = {2022-07-15}, journal = {J. Magn. Magn. Mater.}, volume = {554}, pages = {169260}, abstract = {Mechanical control of electronic and magnetic properties of 2D Van-der-Waals heterostructures gives new possibilities for further development of spintronics and information-related technologies. Using the density functional theory, we investigate the structural, electronic and magnetic properties of silicene monolayer with substituted Chromium atoms and under a small biaxial strain (-6% < e < 8%). Our results indicate that the Cr-doped silicene nanosheets without strain have magnetic metallic, half-metallic or semiconducting properties depending on the type of substitution. We also show that the magnetic moments associated with the monomer and vertical dimer substitutions change very weakly with strain. However, the magnetic moment associated with the horizontal dimer substitution decreases when either compressive or tensile strain is applied to the system. Additionally, we show that the largest semiconductor band-gap is approximately 0.13 eV under zero strain for the vertical Cr-doped silicene. Finally, biaxial compressive strain leads to irregular changes in the magnetic moment for Cr vertical dimer substitution.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Mechanical control of electronic and magnetic properties of 2D Van-der-Waals heterostructures gives new possibilities for further development of spintronics and information-related technologies. Using the density functional theory, we investigate the structural, electronic and magnetic properties of silicene monolayer with substituted Chromium atoms and under a small biaxial strain (-6% < e < 8%). Our results indicate that the Cr-doped silicene nanosheets without strain have magnetic metallic, half-metallic or semiconducting properties depending on the type of substitution. We also show that the magnetic moments associated with the monomer and vertical dimer substitutions change very weakly with strain. However, the magnetic moment associated with the horizontal dimer substitution decreases when either compressive or tensile strain is applied to the system. Additionally, we show that the largest semiconductor band-gap is approximately 0.13 eV under zero strain for the vertical Cr-doped silicene. Finally, biaxial compressive strain leads to irregular changes in the magnetic moment for Cr vertical dimer substitution. |
| 28. | Amir N. Zarezad, Anna Dyrdał Bilinear magnetoresistance in topological insulators: Role of magnetic disorder J. Magn. Magn. Mater., 552 , pp. 169167, 2022, ISSN: 0304-8853. @article{Zarezad2022, title = {Bilinear magnetoresistance in topological insulators: Role of magnetic disorder}, author = {Amir N. Zarezad and Anna Dyrdał}, url = {https://www.sciencedirect.com/science/article/pii/S0304885322001329?via%3Dihub}, doi = {10.1016/j.jmmm.2022.169167}, issn = {0304-8853}, year = {2022}, date = {2022-06-15}, journal = {J. Magn. Magn. Mater.}, volume = {552}, pages = {169167}, abstract = {Bilinear magnetoresistance is a nonlinear transport phenomenon that scales linearly with the electric and magnetic fields, and appears in nonmagnetic systems with strong spin–orbit coupling, such as topological insulators (TIs). Using the semiclassical Boltzmann theory and generalized relaxation time approximation, we consider in detail the bilinear magnetoresistance in an effective model describing surface states of three-dimensional topological insulators. We show that the presence of magnetic impurities remarkably modifies the BMR signal. In general, scattering on magnetic impurities reduces magnitude of BMR. Apart from this, an additional modulation of the angular dependence of BMR appears when the spin-dependent component of the impurity potential dominates the scalar one.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Bilinear magnetoresistance is a nonlinear transport phenomenon that scales linearly with the electric and magnetic fields, and appears in nonmagnetic systems with strong spin–orbit coupling, such as topological insulators (TIs). Using the semiclassical Boltzmann theory and generalized relaxation time approximation, we consider in detail the bilinear magnetoresistance in an effective model describing surface states of three-dimensional topological insulators. We show that the presence of magnetic impurities remarkably modifies the BMR signal. In general, scattering on magnetic impurities reduces magnitude of BMR. Apart from this, an additional modulation of the angular dependence of BMR appears when the spin-dependent component of the impurity potential dominates the scalar one. |
| 27. | Tomasz Ślusarski, Kacper Wrześniewski, Ireneusz Weymann Numerical renormalization group study of the Loschmidt echo in Kondo systems Scientific Reports, 12 , pp. 9799, 2022. @article{Ślusarski2022, title = {Numerical renormalization group study of the Loschmidt echo in Kondo systems}, author = {Tomasz Ślusarski and Kacper Wrześniewski and Ireneusz Weymann}, url = {https://www.nature.com/articles/s41598-022-14108-x}, doi = {10.1038/s41598-022-14108-x}, year = {2022}, date = {2022-06-13}, journal = {Scientific Reports}, volume = {12}, pages = {9799}, abstract = {We study the dynamical properties of the one-channel and two-channel spin-1/2 Kondo models after quenching in Hamiltonian variables. Eigen spectrum of the initial and final Hamiltonians is calculated by using the numerical renormalization group method implemented within the matrix product states formalism. We consider multiple quench protocols in the considered Kondo systems, also in the presence of external magnetic field of different intensities. The main emphasis is put on the analysis of the behavior of the Loschmidt echo L(t), which measures the ability of the system’s revival to its initial state after a quench. We show that the decay of the Loschmidt echo strongly depends on the type of quench and the ground state of the system. For the one-channel Kondo model, we show that L(t) decays as, L(t)∼(t⋅TK)^−1.4, where TK is the Kondo temperature, while for the two-channel Kondo model, we demonstrate that the decay is slower and given by L(t)∼(t⋅TK)^−0.7. In addition, we also determine the dynamical behavior of the impurity’s magnetization, which sheds light on identification of the relevant time scales in the system’s dynamics.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We study the dynamical properties of the one-channel and two-channel spin-1/2 Kondo models after quenching in Hamiltonian variables. Eigen spectrum of the initial and final Hamiltonians is calculated by using the numerical renormalization group method implemented within the matrix product states formalism. We consider multiple quench protocols in the considered Kondo systems, also in the presence of external magnetic field of different intensities. The main emphasis is put on the analysis of the behavior of the Loschmidt echo L(t), which measures the ability of the system’s revival to its initial state after a quench. We show that the decay of the Loschmidt echo strongly depends on the type of quench and the ground state of the system. For the one-channel Kondo model, we show that L(t) decays as, L(t)∼(t⋅TK)^−1.4, where TK is the Kondo temperature, while for the two-channel Kondo model, we demonstrate that the decay is slower and given by L(t)∼(t⋅TK)^−0.7. In addition, we also determine the dynamical behavior of the impurity’s magnetization, which sheds light on identification of the relevant time scales in the system’s dynamics. |
| 26. | Vrishali Sonar, Rohan Dehankar, K. P. Vijayalakshmi, Natalio Mingo, Ankita Katre Site-independent strong phonon-vacancy scattering in high-temperature ceramics ZrB2 and HfB2 Phys. Rev. Materials, 6 , pp. 065403, 2022. @article{Sonar2022, title = {Site-independent strong phonon-vacancy scattering in high-temperature ceramics ZrB2 and HfB2}, author = {Vrishali Sonar and Rohan Dehankar and K. P. Vijayalakshmi and Natalio Mingo and Ankita Katre}, url = {https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.6.065403}, doi = {10.1103/PhysRevMaterials.6.065403}, year = {2022}, date = {2022-06-10}, journal = {Phys. Rev. Materials}, volume = {6}, pages = {065403}, abstract = {Similar effects of metal and boron vacancies on phonon scattering and lattice thermal conductivity (κl) of ZrB2 and HfB2 are reported. These defects challenge the conventional understanding that associates larger impacts to bigger defects. We find the underlying reason to be a strong local perturbation caused by boron vacancy that substantially changes the interatomic force constants. In contrast, a long ranged but weaker perturbation is seen in the case of metal vacancy. We show that these behaviors originate from a mixed metallic and covalent bonding nature in the metal diborides. The thermal transport calculations are performed in a complete ab initio framework based on Boltzmann transport equation and density functional theory. Phonon-vacancy scattering is calculated using ab initio Green's function approach. Effects of natural isotopes and grain boundaries on κl are also systematically investigated, however we find an influential role of vacancies to explain large variations seen in the experiments. We further report a two-order of magnitude difference between the amorphous and pure-crystal limits. Our results outline significant material design aspects for these multifunctional high-temperature ceramics.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Similar effects of metal and boron vacancies on phonon scattering and lattice thermal conductivity (κl) of ZrB2 and HfB2 are reported. These defects challenge the conventional understanding that associates larger impacts to bigger defects. We find the underlying reason to be a strong local perturbation caused by boron vacancy that substantially changes the interatomic force constants. In contrast, a long ranged but weaker perturbation is seen in the case of metal vacancy. We show that these behaviors originate from a mixed metallic and covalent bonding nature in the metal diborides. The thermal transport calculations are performed in a complete ab initio framework based on Boltzmann transport equation and density functional theory. Phonon-vacancy scattering is calculated using ab initio Green's function approach. Effects of natural isotopes and grain boundaries on κl are also systematically investigated, however we find an influential role of vacancies to explain large variations seen in the experiments. We further report a two-order of magnitude difference between the amorphous and pure-crystal limits. Our results outline significant material design aspects for these multifunctional high-temperature ceramics. |
| 25. | Piotr Majek, Ireneusz Weymann Majorana-Kondo competition in a cross-shaped double quantum dot-topological superconductor system Journal of Magnetism and Magnetic Materials, (549), pp. 168935, 2022. @article{Majek2022, title = {Majorana-Kondo competition in a cross-shaped double quantum dot-topological superconductor system}, author = {Piotr Majek and Ireneusz Weymann}, url = {https://www.sciencedirect.com/science/article/abs/pii/S0304885321011331}, doi = {10.1016/j.jmmm.2021.168935}, year = {2022}, date = {2022-05-01}, journal = {Journal of Magnetism and Magnetic Materials}, number = {549}, pages = {168935}, abstract = {We examine the transport properties of a double quantum dot system coupled to a topological superconducting nanowire hosting Majorana quasiparticles at its ends, with the central quantum dot attached to the left and right leads. We focus on the behavior of the local density of states and the linear conductance, calculated with the aid of the numerical renormalization group method, to describe the influence of the Majorana coupling on the low-temperature transport properties induced by the Kondo correlations. In particular, we show that the presence of Majorana quasiparticles in the system affects both the spin-up and spin-down transport channels, affecting the energy scales associated with the first-stage and second-stage Kondo temperatures, respectively, and modifying the low-energy behavior of the system.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We examine the transport properties of a double quantum dot system coupled to a topological superconducting nanowire hosting Majorana quasiparticles at its ends, with the central quantum dot attached to the left and right leads. We focus on the behavior of the local density of states and the linear conductance, calculated with the aid of the numerical renormalization group method, to describe the influence of the Majorana coupling on the low-temperature transport properties induced by the Kondo correlations. In particular, we show that the presence of Majorana quasiparticles in the system affects both the spin-up and spin-down transport channels, affecting the energy scales associated with the first-stage and second-stage Kondo temperatures, respectively, and modifying the low-energy behavior of the system. |
| 24. | Piotr Trocha, Emil Siuda Spin-thermoelectric effects in a quantum dot hybrid system with magnetic insulator Scientific Reports, 12 (5348), 2022. @article{Trocha2022c, title = {Spin-thermoelectric effects in a quantum dot hybrid system with magnetic insulator}, author = {Piotr Trocha and Emil Siuda}, url = {https://www.nature.com/articles/s41598-022-09105-z}, doi = {10.1038/s41598-022-09105-z}, year = {2022}, date = {2022-03-30}, journal = {Scientific Reports}, volume = {12}, number = {5348}, abstract = {We investigate spin thermoelectric properties of a hybrid system consisting of a single-level quantum dot attached to magnetic insulator and metal electrodes. Magnetic insulator is assumed to be of ferromagnetic type and is a source of magnons, whereas metallic lead is reservoir of electrons. The temperature gradient set between the magnetic insulator and metallic electrodes induces the spin current flowing through the system. The generated spin current of magnonic (electric) type is converted to electric (magnonic) spin current by means of quantum dot. Expanding spin and heat currents flowing through the system, up to linear order, we introduce basic spin thermoelectric coefficients including spin conductance, spin Seebeck and spin Peltier coefficients and heat conductance. We analyse the spin thermoelectric properties of the system in two cases: in the large ondot Coulomb repulsion limit and when these interactions are finite.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We investigate spin thermoelectric properties of a hybrid system consisting of a single-level quantum dot attached to magnetic insulator and metal electrodes. Magnetic insulator is assumed to be of ferromagnetic type and is a source of magnons, whereas metallic lead is reservoir of electrons. The temperature gradient set between the magnetic insulator and metallic electrodes induces the spin current flowing through the system. The generated spin current of magnonic (electric) type is converted to electric (magnonic) spin current by means of quantum dot. Expanding spin and heat currents flowing through the system, up to linear order, we introduce basic spin thermoelectric coefficients including spin conductance, spin Seebeck and spin Peltier coefficients and heat conductance. We analyse the spin thermoelectric properties of the system in two cases: in the large ondot Coulomb repulsion limit and when these interactions are finite. |
| 23. | Mir Ali Jafari, Anna Dyrdał Molecules, 27 (7), pp. 2228, 2022, ISSN: 1420-3049. @article{Jafari2022c, title = {First Principle Study on Electronic and Transport Properties of Finite-Length Nanoribbons and Nanodiscs for Selected Two-Dimensional Materials}, author = {Mir Ali Jafari and Anna Dyrdał}, url = {https://www.mdpi.com/1420-3049/27/7/2228}, doi = {10.3390/molecules27072228}, issn = {1420-3049}, year = {2022}, date = {2022-03-29}, journal = {Molecules}, volume = {27}, number = {7}, pages = {2228}, abstract = {Using the density functional theory, we calculate electronic states of various nanoribbons and nanodiscs formed from selected two-dimensional materials, such as graphene, silicene, and hexagonal boron nitride. The main objective of the analysis is a search for zero-energy states in such systems, which is an important issue as their presence indicates certain topological properties associated with chirality. The analysis is also supported by calculating transport properties.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Using the density functional theory, we calculate electronic states of various nanoribbons and nanodiscs formed from selected two-dimensional materials, such as graphene, silicene, and hexagonal boron nitride. The main objective of the analysis is a search for zero-energy states in such systems, which is an important issue as their presence indicates certain topological properties associated with chirality. The analysis is also supported by calculating transport properties. |
| 22. | Kacper Wrześniewski, Ireneusz Weymann, Nicholas Sedlmayr, Tadeusz Domański Dynamical quantum phase transitions in a mesoscopic superconducting system Phys. Rev. B, 105 , pp. 094514, 2022. @article{Wrześniewski2022c, title = {Dynamical quantum phase transitions in a mesoscopic superconducting system}, author = {Kacper Wrześniewski and Ireneusz Weymann and Nicholas Sedlmayr and Tadeusz Domański}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.105.094514}, doi = {10.1103/PhysRevB.105.094514}, year = {2022}, date = {2022-03-25}, journal = {Phys. Rev. B}, volume = {105}, pages = {094514}, abstract = {We inspect the signatures of dynamical quantum phase transitions driven by quantum quenches acting on a correlated quantum dot embedded between superconducting and metallic reservoirs. Under stationary conditions, the proximity-induced electron pairing, competing with strong Coulomb repulsion, enforces the quantum dot to be either in the singly occupied or BCS-type ground state, depending on its energy level and coupling to the superconducting lead. By means of the time-dependent numerical renormalization group approach, we study the system's time evolution upon traversing the phase boundary between these two states, examining the Loschmidt echo and revealing nonanalytic features in the low-energy return rate, which signal dynamical quantum phase transitions. We also show that these phase transitions are accompanied by the corresponding local extrema in the pairing correlation function and dot's occupation. Since the proposed quench protocols can be realized in a controllable manner, the detection of this dynamical singlet-doublet phase transition should be feasible by performing tunneling spectroscopy measurements.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We inspect the signatures of dynamical quantum phase transitions driven by quantum quenches acting on a correlated quantum dot embedded between superconducting and metallic reservoirs. Under stationary conditions, the proximity-induced electron pairing, competing with strong Coulomb repulsion, enforces the quantum dot to be either in the singly occupied or BCS-type ground state, depending on its energy level and coupling to the superconducting lead. By means of the time-dependent numerical renormalization group approach, we study the system's time evolution upon traversing the phase boundary between these two states, examining the Loschmidt echo and revealing nonanalytic features in the low-energy return rate, which signal dynamical quantum phase transitions. We also show that these phase transitions are accompanied by the corresponding local extrema in the pairing correlation function and dot's occupation. Since the proposed quench protocols can be realized in a controllable manner, the detection of this dynamical singlet-doublet phase transition should be feasible by performing tunneling spectroscopy measurements. |
| 21. | Mir Ali Jafari, Małgorzata Wawrzyniak-Adamczewska, Stefan Stagraczyński, Anna Dyrdał, Józef Barnaś Spin valve effect in two-dimensional VSe2 system J. Magn. Magn. Mater., 548 , pp. 168921, 2022, ISSN: 0304-8853. @article{Jafari2022, title = {Spin valve effect in two-dimensional VSe2 system}, author = {Mir Ali Jafari and Małgorzata Wawrzyniak-Adamczewska and Stefan Stagraczyński and Anna Dyrdał and Józef Barnaś}, url = {https://www.sciencedirect.com/science/article/pii/S0304885321011215?via%3Dihub}, doi = {10.1016/j.jmmm.2021.168921}, issn = {0304-8853}, year = {2022}, date = {2022-03-15}, journal = {J. Magn. Magn. Mater.}, volume = {548}, pages = {168921}, abstract = {Vanadium based dichalcogenides, VSe2, are two-dimensional materials in which magnetic Vanadium atoms are arranged in a hexagonal lattice and are coupled ferromagnetically within the plane. However, adjacent atomic planes are coupled antiferromagnetically. This provides new and interesting opportunities for application in spintronics and data storage and processing technologies. A spin valve magnetoresistance may be achieved when magnetic moments of both atomic planes are driven to parallel alignment by an external magnetic field. The resistance change associated with the transition from antiparallel to parallel configuration is qualitatively similar to that observed in artificially layered metallic magnetic structures. Detailed electronic structure of VSe2 was obtained from DFT calculations. Then, the ballistic spin-valve magnetoresistance was determined within the Landauer formalism. In addition, we also analyze thermal and thermoelectric properties. Both phases of VSe2, denoted as H and T, are considered.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Vanadium based dichalcogenides, VSe2, are two-dimensional materials in which magnetic Vanadium atoms are arranged in a hexagonal lattice and are coupled ferromagnetically within the plane. However, adjacent atomic planes are coupled antiferromagnetically. This provides new and interesting opportunities for application in spintronics and data storage and processing technologies. A spin valve magnetoresistance may be achieved when magnetic moments of both atomic planes are driven to parallel alignment by an external magnetic field. The resistance change associated with the transition from antiparallel to parallel configuration is qualitatively similar to that observed in artificially layered metallic magnetic structures. Detailed electronic structure of VSe2 was obtained from DFT calculations. Then, the ballistic spin-valve magnetoresistance was determined within the Landauer formalism. In addition, we also analyze thermal and thermoelectric properties. Both phases of VSe2, denoted as H and T, are considered. |
| 20. | Patrycja Tulewicz, Kacper Wrześniewski, Ireneusz Weymann Spintronic transport through a double quantum dot-based spin valve with noncollinear magnetizations Journal of Magnetism and Magnetic Materials, 546 , pp. 168788, 2022. @article{Tulewicz2022, title = {Spintronic transport through a double quantum dot-based spin valve with noncollinear magnetizations}, author = {Patrycja Tulewicz and Kacper Wrześniewski and Ireneusz Weymann}, url = {https://www.sciencedirect.com/science/article/pii/S0304885321010118}, doi = {10.1016/j.jmmm.2021.168788}, year = {2022}, date = {2022-03-15}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {546}, pages = {168788}, abstract = {We study the magnetoresistive properties of a spin valve based on a double quantum dot attached to ferromagnetic leads with noncollinear alignment of magnetic moments. It is assumed that each dot is strongly coupled to its own ferromagnetic electrode, while the hopping between the dots is relatively weak. The calculations are performed by using the perturbation theory in the coupling between the dots, while the local density of states of a quantum dot attached to a given external lead is determined with the aid of the numerical renormalization group method. We demonstrate that the examined device can exhibit considerable positive or inverse tunnel magnetoresistance. It can be also a source of highly spin-polarized current. Importantly, the spin-resolved transport properties can be controlled by gate and bias voltages and depend on the angle between the magnetizations of the ferromagnets.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We study the magnetoresistive properties of a spin valve based on a double quantum dot attached to ferromagnetic leads with noncollinear alignment of magnetic moments. It is assumed that each dot is strongly coupled to its own ferromagnetic electrode, while the hopping between the dots is relatively weak. The calculations are performed by using the perturbation theory in the coupling between the dots, while the local density of states of a quantum dot attached to a given external lead is determined with the aid of the numerical renormalization group method. We demonstrate that the examined device can exhibit considerable positive or inverse tunnel magnetoresistance. It can be also a source of highly spin-polarized current. Importantly, the spin-resolved transport properties can be controlled by gate and bias voltages and depend on the angle between the magnetizations of the ferromagnets. |