List of publications
Department of Mesoscopic Physics
Department of Nonlinear Optics
Department of Physics of Nanostructures
Department of Theory of Condensed Matter
2021 |
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| 36. | Damian Tomaszewski, Piotr Busz, Jan Martinek Spin-current Kondo effect: Kondo effect in the presence of spin accumulation Phys. Rev. B, 104 , pp. 125108, 2021. @article{Tomaszewski2021, title = {Spin-current Kondo effect: Kondo effect in the presence of spin accumulation}, author = {Damian Tomaszewski and Piotr Busz and Jan Martinek}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.104.125108}, doi = {10.1103/PhysRevB.104.125108}, year = {2021}, date = {2021-09-07}, journal = {Phys. Rev. B}, volume = {104}, pages = {125108}, abstract = {We present a detailed theoretical description of the influence of the spin accumulation in metallic Fermi leads on the Kondo effect in systems such as quantum dots and Kondo alloys. We discuss an interplay of the spin accumulation, magnetic field, and ferromagnetic leads spin polarization on the Kondo spin-dependent densities of states, conductance, and resistance. It has been shown that the presence of the above-mentioned factors by breaking the spin symmetry leads to the suppression of the Kondo effect. However, for appropriately selected parameter values, these effects can compensate each other, which may lead to the restoration of the Kondo effect in the analyzed systems. We also address some recent experiments related to the spin current in the Kondo alloys.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a detailed theoretical description of the influence of the spin accumulation in metallic Fermi leads on the Kondo effect in systems such as quantum dots and Kondo alloys. We discuss an interplay of the spin accumulation, magnetic field, and ferromagnetic leads spin polarization on the Kondo spin-dependent densities of states, conductance, and resistance. It has been shown that the presence of the above-mentioned factors by breaking the spin symmetry leads to the suppression of the Kondo effect. However, for appropriately selected parameter values, these effects can compensate each other, which may lead to the restoration of the Kondo effect in the analyzed systems. We also address some recent experiments related to the spin current in the Kondo alloys. |
| 35. | Wei Qin, Adam Miranowicz, Hui Jing, Franco Nori Generating Long-Lived Macroscopically Distinct Superposition States in Atomic Ensembles Phys. Rev. Lett., 127 , pp. 093602, 2021. @article{Qin2021, title = {Generating Long-Lived Macroscopically Distinct Superposition States in Atomic Ensembles}, author = {Wei Qin and Adam Miranowicz and Hui Jing and Franco Nori}, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.093602}, doi = {10.1103/PhysRevLett.127.093602}, year = {2021}, date = {2021-08-23}, journal = {Phys. Rev. Lett.}, volume = {127}, pages = {093602}, abstract = {We propose to create and stabilize long-lived macroscopic quantum superposition states in atomic ensembles. We show that using a fully quantum parametric amplifier can cause the simultaneous decay of two atoms and, in turn, create stabilized atomic Schrödinger cat states. Remarkably, even with modest parameters these intracavity atomic cat states can have an extremely long lifetime, up to 4 orders of magnitude longer than that of intracavity photonic cat states under the same parameter conditions, reaching tens of milliseconds. This lifetime of atomic cat states is ultimately limited to several seconds by extremely weak spin relaxation and thermal noise. Our work opens up a new way toward the long-standing goal of generating large-size and long-lived cat states, with immediate interests both in fundamental studies and noise-immune quantum technologies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We propose to create and stabilize long-lived macroscopic quantum superposition states in atomic ensembles. We show that using a fully quantum parametric amplifier can cause the simultaneous decay of two atoms and, in turn, create stabilized atomic Schrödinger cat states. Remarkably, even with modest parameters these intracavity atomic cat states can have an extremely long lifetime, up to 4 orders of magnitude longer than that of intracavity photonic cat states under the same parameter conditions, reaching tens of milliseconds. This lifetime of atomic cat states is ultimately limited to several seconds by extremely weak spin relaxation and thermal noise. Our work opens up a new way toward the long-standing goal of generating large-size and long-lived cat states, with immediate interests both in fundamental studies and noise-immune quantum technologies. |
| 34. | Anjan Barman, Gianluca Gubbiotti, S Ladak, A O Adeyeye, Maciej Krawczyk, J Gräfe, C Adelmann, S Cotofana, A Naeemi, V I Vasyuchka, B Hillebrands, S A Nikitov, H Yu, D Grundler, A V Sadovnikov, A A Grachev, S E Sheshukova, J-Y Duquesne, M Marangolo, G Csaba, W Porod, V E Demidov, S Urazhdin, S O Demokritov, E Albisetti, D Petti, R Bertacco, H Schultheiss, V V Kruglyak, V D Poimanov, S Sahoo, J Sinha, H Yang, M Münzenberg, T Moriyama, S Mizukami, P Landeros, R A Gallardo, G Carlotti, J-V Kim, R L Stamps, R E Camley, Bivas Rana, Y Otani, W Yu, T Yu, G E W Bauer, C Back, G S Uhrig, O V Dobrovolskiy, B Budinska, H Qin, S van Dijken, A V Chumak, A Khitun, D E Nikonov, I A Young, B W Zingsem, M Winklhofer Journal of Physics: Condensed Matter, 33 (41), pp. 413001, 2021. @article{Barman_2021, title = {The 2021 Magnonics Roadmap}, author = {Anjan Barman and Gianluca Gubbiotti and S Ladak and A O Adeyeye and Maciej Krawczyk and J Gräfe and C Adelmann and S Cotofana and A Naeemi and V I Vasyuchka and B Hillebrands and S A Nikitov and H Yu and D Grundler and A V Sadovnikov and A A Grachev and S E Sheshukova and J-Y Duquesne and M Marangolo and G Csaba and W Porod and V E Demidov and S Urazhdin and S O Demokritov and E Albisetti and D Petti and R Bertacco and H Schultheiss and V V Kruglyak and V D Poimanov and S Sahoo and J Sinha and H Yang and M Münzenberg and T Moriyama and S Mizukami and P Landeros and R A Gallardo and G Carlotti and J-V Kim and R L Stamps and R E Camley and Bivas Rana and Y Otani and W Yu and T Yu and G E W Bauer and C Back and G S Uhrig and O V Dobrovolskiy and B Budinska and H Qin and S van Dijken and A V Chumak and A Khitun and D E Nikonov and I A Young and B W Zingsem and M Winklhofer}, url = {https://doi.org/10.1088/1361-648x/abec1a}, doi = {10.1088/1361-648x/abec1a}, year = {2021}, date = {2021-08-18}, journal = {Journal of Physics: Condensed Matter}, volume = {33}, number = {41}, pages = {413001}, publisher = {IOP Publishing}, abstract = {Magnonics is a budding research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. The rapid advancements of this field during last one decade in terms of upsurge in research papers, review articles, citations, proposals of devices as well as introduction of new sub-topics prompted us to present the first roadmap on magnonics. This is a collection of 22 sections written by leading experts in this field who review and discuss the current status besides presenting their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and its interconnections to standard electronics. To this end, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This roadmap asserts a milestone for future emerging research directions in magnonics, and hopefully, it will inspire a series of exciting new articles on the same topic in the coming years.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Magnonics is a budding research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. The rapid advancements of this field during last one decade in terms of upsurge in research papers, review articles, citations, proposals of devices as well as introduction of new sub-topics prompted us to present the first roadmap on magnonics. This is a collection of 22 sections written by leading experts in this field who review and discuss the current status besides presenting their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and its interconnections to standard electronics. To this end, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This roadmap asserts a milestone for future emerging research directions in magnonics, and hopefully, it will inspire a series of exciting new articles on the same topic in the coming years. |
| 33. | Marcin Markiewicz, Marcin Karczewski, Paweł Kurzyński Borromean states in discrete-time quantum walks Quantum, 5 , pp. 523, 2021. @article{Markiewicz2021, title = {Borromean states in discrete-time quantum walks}, author = {Marcin Markiewicz and Marcin Karczewski and Paweł Kurzyński}, url = {https://quantum-journal.org/papers/q-2021-08-16-523/}, doi = {10.22331/q-2021-08-16-523}, year = {2021}, date = {2021-08-16}, journal = {Quantum}, volume = {5}, pages = {523}, abstract = {In the right conditions, removing one particle from a multipartite bound state can make it fall apart. This feature, known as the "Borromean property", has been recently demonstrated experimentally in Efimov states. One could expect that such peculiar behavior should be linked with the presence of strong inter-particle correlations. However, any exploration of this connection is hindered by the complexity of the physical systems exhibiting the Borromean property. To overcome this problem, we introduce a simple dynamical toy model based on a discrete-time quantum walk of many interacting particles. We show that the particles described by it need to exhibit the Greenberger-Horne-Zeillinger (GHZ) entanglement to form Borromean bound states. As this type of entanglement is very prone to particle losses, our work demonstrates an intuitive link between correlations and Borromean properties of the system. Moreover, we discuss our findings in the context of the formation of composite particles.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In the right conditions, removing one particle from a multipartite bound state can make it fall apart. This feature, known as the "Borromean property", has been recently demonstrated experimentally in Efimov states. One could expect that such peculiar behavior should be linked with the presence of strong inter-particle correlations. However, any exploration of this connection is hindered by the complexity of the physical systems exhibiting the Borromean property. To overcome this problem, we introduce a simple dynamical toy model based on a discrete-time quantum walk of many interacting particles. We show that the particles described by it need to exhibit the Greenberger-Horne-Zeillinger (GHZ) entanglement to form Borromean bound states. As this type of entanglement is very prone to particle losses, our work demonstrates an intuitive link between correlations and Borromean properties of the system. Moreover, we discuss our findings in the context of the formation of composite particles. |
| 32. | Piotr Majek, Ireneusz Weymann Majorana mode leaking into a spin-charge entangled double quantum dot Phys. Rev. B, 104 , pp. 085416, 2021. @article{Majek2021, title = {Majorana mode leaking into a spin-charge entangled double quantum dot}, author = {Piotr Majek and Ireneusz Weymann}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.104.085416}, doi = {10.1103/PhysRevB.104.085416}, year = {2021}, date = {2021-08-12}, journal = {Phys. Rev. B}, volume = {104}, pages = {085416}, abstract = {The signatures of Majorana zero-energy mode leaking into a spin-charge entangled double quantum dot are investigated theoretically in the strong electron correlation regime. The considered setup consists of two capacitively coupled quantum dots attached to external contacts and side-attached to topological superconducting wire hosting Majorana quasiparticles. We show that the presence of Majorana mode gives rise to unique features in the local density of states in the SU(4) Kondo regime. Moreover, it greatly modifies the gate voltage dependence of the linear conductance, leading to fractional values of the conductance. We also analyze the effect of a finite length of topological wire and demonstrate that nonzero overlap of Majorana modes at the ends of the wire is revealed in local extrema present in the local density of states of the dot coupled directly to the wire. The calculations are performed with the aid of the numerical renormalization group method.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The signatures of Majorana zero-energy mode leaking into a spin-charge entangled double quantum dot are investigated theoretically in the strong electron correlation regime. The considered setup consists of two capacitively coupled quantum dots attached to external contacts and side-attached to topological superconducting wire hosting Majorana quasiparticles. We show that the presence of Majorana mode gives rise to unique features in the local density of states in the SU(4) Kondo regime. Moreover, it greatly modifies the gate voltage dependence of the linear conductance, leading to fractional values of the conductance. We also analyze the effect of a finite length of topological wire and demonstrate that nonzero overlap of Majorana modes at the ends of the wire is revealed in local extrema present in the local density of states of the dot coupled directly to the wire. The calculations are performed with the aid of the numerical renormalization group method. |
| 31. | Veysel Erçağlar, Hodjat Hajian, Andriy E. Serebryannikov, Ekmel Ozbay Multifunctional tunable gradient metasurfaces for terahertz beam splitting and light absorption Opt. Lett., 46 (16), pp. 3953–3956, 2021. @article{Ercaglar:21, title = {Multifunctional tunable gradient metasurfaces for terahertz beam splitting and light absorption}, author = {Veysel Erçağlar and Hodjat Hajian and Andriy E. Serebryannikov and Ekmel Ozbay}, url = {http://ol.osa.org/abstract.cfm?URI=ol-46-16-3953}, doi = {10.1364/OL.435197}, year = {2021}, date = {2021-08-09}, journal = {Opt. Lett.}, volume = {46}, number = {16}, pages = {3953--3956}, publisher = {OSA}, abstract = {Obtaining functional devices with tunable features is beneficial to advance terahertz (THz) science and technology. Here, we propose multifunctional gradient metasurfaces that are composed of a periodic array of binary Si microcylinders integrated with VO2 and graphene. The metasurfaces act as transmittive (reflective) beamsplitters for the dielectric (metallic) phase of VO2 with a switchable characteristic. Moreover, by integrating the metasurfaces with graphene and modifying its chemical potential, one can tune the intensity of the split beam as well as obtain nearly perfect resonant absorptions. Consequently, the proposed metasurfaces can find potential applications in THz interferometers, multiplexers, and light absorbers.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Obtaining functional devices with tunable features is beneficial to advance terahertz (THz) science and technology. Here, we propose multifunctional gradient metasurfaces that are composed of a periodic array of binary Si microcylinders integrated with VO2 and graphene. The metasurfaces act as transmittive (reflective) beamsplitters for the dielectric (metallic) phase of VO2 with a switchable characteristic. Moreover, by integrating the metasurfaces with graphene and modifying its chemical potential, one can tune the intensity of the split beam as well as obtain nearly perfect resonant absorptions. Consequently, the proposed metasurfaces can find potential applications in THz interferometers, multiplexers, and light absorbers. |
| 30. | Piotr Graczyk, Maciej Krawczyk Scientific Reports, 11 (1), pp. 15692, 2021. @article{graczyk_nonresonant_2021, title = {Nonresonant amplification of spin waves through interface magnetoelectric effect and spin-transfer torque}, author = {Piotr Graczyk and Maciej Krawczyk}, url = {https://www.nature.com/articles/s41598-021-95267-1}, doi = {10.1038/s41598-021-95267-1}, year = {2021}, date = {2021-08-03}, urldate = {2021-08-03}, journal = {Scientific Reports}, volume = {11}, number = {1}, pages = {15692}, abstract = {We present a new mechanism for manipulation of the spin-wave amplitude through the use of the dynamic charge-mediated magnetoelectric effect in ultrathin multilayers composed of dielectric thin-film capacitors separated by a ferromagnetic bilayer. Propagating spin waves can be amplified and attenuated with rising and decreasing slopes of the oscillating voltage, respectively, locally applied to the sample. The way the spin accumulation is generated makes the interaction of the spin-transfer torque with the magnetization dynamics mode-selective and restricted to some range of spin-wave frequencies, which is contrary to known types of the spin-transfer torque effects. The interfacial nature of spin-dependent screening allows to reduce the thickness of the fixed magnetization layer to a few nanometers, thus the proposed effect significantly contributes toward realization of the magnonic devices and also miniaturization of the spintronic devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a new mechanism for manipulation of the spin-wave amplitude through the use of the dynamic charge-mediated magnetoelectric effect in ultrathin multilayers composed of dielectric thin-film capacitors separated by a ferromagnetic bilayer. Propagating spin waves can be amplified and attenuated with rising and decreasing slopes of the oscillating voltage, respectively, locally applied to the sample. The way the spin accumulation is generated makes the interaction of the spin-transfer torque with the magnetization dynamics mode-selective and restricted to some range of spin-wave frequencies, which is contrary to known types of the spin-transfer torque effects. The interfacial nature of spin-dependent screening allows to reduce the thickness of the fixed magnetization layer to a few nanometers, thus the proposed effect significantly contributes toward realization of the magnonic devices and also miniaturization of the spintronic devices. |
| 29. | Xiao-Xiao Chen, Zhe Meng, Jian Li, Jia-Zhi Yang, An-Ning Zhang, Tomasz Kopyciuk, Paweł Kurzyński Nonclassical oscillations in pre- and post-selected quantum walks Phys. Rev. A, 104 , pp. 012220, 2021. @article{PhysRevA.104.012220, title = {Nonclassical oscillations in pre- and post-selected quantum walks}, author = {Xiao-Xiao Chen and Zhe Meng and Jian Li and Jia-Zhi Yang and An-Ning Zhang and Tomasz Kopyciuk and Paweł Kurzyński}, url = {https://link.aps.org/doi/10.1103/PhysRevA.104.012220}, doi = {10.1103/PhysRevA.104.012220}, year = {2021}, date = {2021-07-28}, journal = {Phys. Rev. A}, volume = {104}, pages = {012220}, publisher = {American Physical Society}, abstract = {Quantum walks are counterparts of classical random walks. They spread faster, which can be exploited in information processing tasks, and constitute a versatile simulation platform for many quantum systems. Yet, some of their properties can be emulated with classical light. This raises a question: which aspects of the model are truly nonclassical? We address it by carrying out a photonic experiment based on a pre- and post-selection paradox. The paradox implies that if somebody could choose to ask either if the particle is at position x = 0 at even time steps or at position x = d (d > 1) at odd time steps, the answer would be positive, no matter the question asked. Therefore, the particle seems to undergo long distance oscillations despite the fact that the model allows it to jump one position at a time. We translate this paradox into a Bell-like inequality and then into a contextuality witness. Finally, we experimentally verify this witness up to eight standard deviations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Quantum walks are counterparts of classical random walks. They spread faster, which can be exploited in information processing tasks, and constitute a versatile simulation platform for many quantum systems. Yet, some of their properties can be emulated with classical light. This raises a question: which aspects of the model are truly nonclassical? We address it by carrying out a photonic experiment based on a pre- and post-selection paradox. The paradox implies that if somebody could choose to ask either if the particle is at position x = 0 at even time steps or at position x = d (d > 1) at odd time steps, the answer would be positive, no matter the question asked. Therefore, the particle seems to undergo long distance oscillations despite the fact that the model allows it to jump one position at a time. We translate this paradox into a Bell-like inequality and then into a contextuality witness. Finally, we experimentally verify this witness up to eight standard deviations. |
| 28. | Aleksandra Trzaskowska, Sławomir Mielcarek, M Wiesner, F Lombardi, Bogusław Mróz Ultrasonics, 117 , pp. 106526, 2021. @article{TRZASKOWSKA2021106526, title = {Dispersion of the surface phonons in semiconductor/topological insulator Si/Bi2Te3 heterostructure studied by high resolution Brillouin spectroscopy}, author = {Aleksandra Trzaskowska and Sławomir Mielcarek and M Wiesner and F Lombardi and Bogusław Mróz}, url = {https://www.sciencedirect.com/science/article/pii/S0041624X21001554}, doi = {https://doi.org/10.1016/j.ultras.2021.106526}, year = {2021}, date = {2021-07-21}, journal = {Ultrasonics}, volume = {117}, pages = {106526}, abstract = {The dynamics and dispersion of surface phonons in heterostructure semiconductor/ topological insulator Si/Bi2Te3 was investigated using high resolution Brillouin light scattering method in the GHz frequency range. Both Rayleigh and Sezawa surface acoustic waves have been observed for wave vectors ranging from 0.006 to 0.023 nm−1. Anomaly in dispersion relations ω(q) for both surface waves were detected for the wave vector q = 0.016 nm−1. The finite element method (FEM) was used to simulate the observed shapes of ω(q) and to find the deformation profiles of surface acoustic waves. We attribute the observed changes to the coupling between low energy electrons and surface phonons. The coupling between helical Dirac states and surface phonons is discussed in the frame of accessible theoretical models.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The dynamics and dispersion of surface phonons in heterostructure semiconductor/ topological insulator Si/Bi2Te3 was investigated using high resolution Brillouin light scattering method in the GHz frequency range. Both Rayleigh and Sezawa surface acoustic waves have been observed for wave vectors ranging from 0.006 to 0.023 nm−1. Anomaly in dispersion relations ω(q) for both surface waves were detected for the wave vector q = 0.016 nm−1. The finite element method (FEM) was used to simulate the observed shapes of ω(q) and to find the deformation profiles of surface acoustic waves. We attribute the observed changes to the coupling between low energy electrons and surface phonons. The coupling between helical Dirac states and surface phonons is discussed in the frame of accessible theoretical models. |
| 27. | Pontus Laurell, Allen Scheie, Chiron J Mukherjee, Michael M Koza, Mechtild Enderle, Zbigniew Tylczyński, Satoshi Okamoto, Radu Coldea, Alan D Tennant, Gonzalo Alvarez Quantifying and Controlling Entanglement in the Quantum Magnet Cs2CoCl4 Phys. Rev. Lett., 127 , pp. 037201, 2021. @article{PhysRevLett.127.037201, title = {Quantifying and Controlling Entanglement in the Quantum Magnet Cs2CoCl4}, author = {Pontus Laurell and Allen Scheie and Chiron J Mukherjee and Michael M Koza and Mechtild Enderle and Zbigniew Tylczyński and Satoshi Okamoto and Radu Coldea and Alan D Tennant and Gonzalo Alvarez}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.127.037201}, doi = {10.1103/PhysRevLett.127.037201}, year = {2021}, date = {2021-07-13}, journal = {Phys. Rev. Lett.}, volume = {127}, pages = {037201}, publisher = {American Physical Society}, abstract = {The lack of methods to experimentally detect and quantify entanglement in quantum matter impedes our ability to identify materials hosting highly entangled phases, such as quantum spin liquids. We thus investigate the feasibility of using inelastic neutron scattering (INS) to implement a model-independent measurement protocol for entanglement based on three entanglement witnesses: one-tangle, two-tangle, and quantum Fisher information (QFI). We perform high-resolution INS measurements on Cs2CoCl4, a close realization of the S=1/2 transverse-field XXZ spin chain, where we can control entanglement using the magnetic field, and compare with density-matrix renormalization group calculations for validation. The three witnesses allow us to infer entanglement properties and make deductions about the quantum state in the material. We find QFI to be a particularly robust experimental probe of entanglement, whereas the one and two-tangles require more careful analysis. Our results lay the foundation for a general entanglement detection protocol for quantum spin systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The lack of methods to experimentally detect and quantify entanglement in quantum matter impedes our ability to identify materials hosting highly entangled phases, such as quantum spin liquids. We thus investigate the feasibility of using inelastic neutron scattering (INS) to implement a model-independent measurement protocol for entanglement based on three entanglement witnesses: one-tangle, two-tangle, and quantum Fisher information (QFI). We perform high-resolution INS measurements on Cs2CoCl4, a close realization of the S=1/2 transverse-field XXZ spin chain, where we can control entanglement using the magnetic field, and compare with density-matrix renormalization group calculations for validation. The three witnesses allow us to infer entanglement properties and make deductions about the quantum state in the material. We find QFI to be a particularly robust experimental probe of entanglement, whereas the one and two-tangles require more careful analysis. Our results lay the foundation for a general entanglement detection protocol for quantum spin systems. |
| 26. | Patrycja Tulewicz, Kacper Wrześniewski, Szabolcs Csonka, Ireneusz Weymann Large Voltage-Tunable Spin Valve Based on a Double Quantum Dot Phys. Rev. Applied, 16 , pp. 014029, 2021. @article{Tulewicz2021, title = {Large Voltage-Tunable Spin Valve Based on a Double Quantum Dot}, author = {Patrycja Tulewicz and Kacper Wrześniewski and Szabolcs Csonka and Ireneusz Weymann}, url = {https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.16.014029}, doi = {https://doi.org/10.1103/PhysRevApplied.16.014029}, year = {2021}, date = {2021-07-12}, journal = {Phys. Rev. Applied}, volume = {16}, pages = {014029}, abstract = {We study the spin-dependent transport properties of a spin valve based on a double quantum dot. Each quantum dot is assumed to be strongly coupled to its own ferromagnetic lead, while the coupling between the dots is relatively weak. The current flowing through the system is determined within perturbation theory in the hopping between the dots, whereas the spectrum of a quantum-dot–ferromagnetic-lead subsystem is determined by means of the numerical renormalization group method. The spin-dependent charge fluctuations between ferromagnets and quantum dots generate an effective exchange field, which splits the double-dot levels. Such a field can be controlled, separately for each quantum dot, by the gate voltages or by changing the magnetic configuration of the external leads. We demonstrate that the considered double-quantum-dot spin-valve setup exhibits enhanced magnetoresistive properties, including both normal and inverse tunnel magnetoresistance. We also show that this system allows for the generation of highly spin-polarized currents, which can be controlled by purely electrical means. The considered double quantum dot with ferromagnetic contacts can thus serve as an efficient voltage-tunable spin valve characterized by high output parameters.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We study the spin-dependent transport properties of a spin valve based on a double quantum dot. Each quantum dot is assumed to be strongly coupled to its own ferromagnetic lead, while the coupling between the dots is relatively weak. The current flowing through the system is determined within perturbation theory in the hopping between the dots, whereas the spectrum of a quantum-dot–ferromagnetic-lead subsystem is determined by means of the numerical renormalization group method. The spin-dependent charge fluctuations between ferromagnets and quantum dots generate an effective exchange field, which splits the double-dot levels. Such a field can be controlled, separately for each quantum dot, by the gate voltages or by changing the magnetic configuration of the external leads. We demonstrate that the considered double-quantum-dot spin-valve setup exhibits enhanced magnetoresistive properties, including both normal and inverse tunnel magnetoresistance. We also show that this system allows for the generation of highly spin-polarized currents, which can be controlled by purely electrical means. The considered double quantum dot with ferromagnetic contacts can thus serve as an efficient voltage-tunable spin valve characterized by high output parameters. |
| 25. | Ievgen I Arkhipov, Fabrizio Minganti, Adam Miranowicz, Franco Nori Generating high-order quantum exceptional points in synthetic dimensions Physical Review A, 104 (1), pp. 012205, 2021. @article{Arkhipov2021b, title = {Generating high-order quantum exceptional points in synthetic dimensions}, author = {Ievgen I Arkhipov and Fabrizio Minganti and Adam Miranowicz and Franco Nori}, url = {https://doi.org/10.1103/physreva.104.012205}, doi = {10.1103/physreva.104.012205}, year = {2021}, date = {2021-07-08}, journal = {Physical Review A}, volume = {104}, number = {1}, pages = {012205}, publisher = {American Physical Society (APS)}, abstract = {Recently, there has been intense research in proposing and developing various methods for constructing high-order exceptional points (EPs) in dissipative systems. These EPs can possess a number of intriguing properties related to, e.g., chiral transport and enhanced sensitivity. Previous proposals to realize non-Hermitian Hamiltonians (NHHs) with high-order EPs have been mainly based on either direct construction of spatial networks of coupled modes or utilization of synthetic dimensions, e.g., mapping of spatial lattices to time or photon-number space. Both methods rely on the construction of effective NHHs describing classical or postselected quantum fields, which neglect the effects of quantum jumps and which, thus, suffer from a scalability problem in the quantum regime, when the probability of quantum jumps increases with the number of excitations and dissipation rate. Here, by considering the full quantum dynamics of a quadratic Liouvillian superoperator, we introduce a simple and effective method for engineering NHHs with high-order quantum EPs, derived from evolution matrices of system operator moments. That is, by quantizing higher-order moments of system operators, e.g., of a quadratic two-mode system, the resulting evolution matrices can be interpreted as alternative NHHs describing, e.g., a spatial lattice of coupled resonators, where spatial sites are represented by high-order field moments in the synthetic space of field moments. Notably, such a mapping allows correct reproduction of the results of the Liouvillian dynamics, including quantum jumps. As an example, we consider a U(1)-symmetric quadratic Liouvillian describing a bimodal cavity with incoherent mode coupling, which can also possess anti−PT symmetry, whose field moment dynamics can be mapped to an NHH governing a spatial network of coupled resonators with high-order EPs.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Recently, there has been intense research in proposing and developing various methods for constructing high-order exceptional points (EPs) in dissipative systems. These EPs can possess a number of intriguing properties related to, e.g., chiral transport and enhanced sensitivity. Previous proposals to realize non-Hermitian Hamiltonians (NHHs) with high-order EPs have been mainly based on either direct construction of spatial networks of coupled modes or utilization of synthetic dimensions, e.g., mapping of spatial lattices to time or photon-number space. Both methods rely on the construction of effective NHHs describing classical or postselected quantum fields, which neglect the effects of quantum jumps and which, thus, suffer from a scalability problem in the quantum regime, when the probability of quantum jumps increases with the number of excitations and dissipation rate. Here, by considering the full quantum dynamics of a quadratic Liouvillian superoperator, we introduce a simple and effective method for engineering NHHs with high-order quantum EPs, derived from evolution matrices of system operator moments. That is, by quantizing higher-order moments of system operators, e.g., of a quadratic two-mode system, the resulting evolution matrices can be interpreted as alternative NHHs describing, e.g., a spatial lattice of coupled resonators, where spatial sites are represented by high-order field moments in the synthetic space of field moments. Notably, such a mapping allows correct reproduction of the results of the Liouvillian dynamics, including quantum jumps. As an example, we consider a U(1)-symmetric quadratic Liouvillian describing a bimodal cavity with incoherent mode coupling, which can also possess anti−PT symmetry, whose field moment dynamics can be mapped to an NHH governing a spatial network of coupled resonators with high-order EPs. |
| 24. | T F Gundogdu, M Gokkavas, Andriy E. Serebryannikov, E Ozbay Evidence of asymmetric beaming in a piecewise-linear propagation channel Opt. Lett., 46 (12), pp. 2928–2931, 2021. @article{Gundogdu:21, title = {Evidence of asymmetric beaming in a piecewise-linear propagation channel}, author = {T F Gundogdu and M Gokkavas and Andriy E. Serebryannikov and E Ozbay}, url = {https://opg.optica.org/ol/abstract.cfm?URI=ol-46-12-2928}, doi = {10.1364/OL.420297}, year = {2021}, date = {2021-06-14}, journal = {Opt. Lett.}, volume = {46}, number = {12}, pages = {2928--2931}, publisher = {Optica Publishing Group}, abstract = {Asymmetric beaming in a piecewise-linear propagation channel is demonstrated for a single photonic-crystal prism at Gaussian-beam illumination. The used hybrid refraction--diffraction mechanism exploits oblique incidence, the first-negative-order deflection at the longer interface, and asymmetry in coupling at the exit interfaces and does not need blocking of transmission by dispersion in the backward illumination case. The Floquet--Bloch mode with left-handed behavior and nearly circular equifrequency dispersion contours is utilized. The outgoing waves may have significantly different spatial distributions for the forward and backward illumination cases, yielding asymmetry in the beaming regime.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Asymmetric beaming in a piecewise-linear propagation channel is demonstrated for a single photonic-crystal prism at Gaussian-beam illumination. The used hybrid refraction--diffraction mechanism exploits oblique incidence, the first-negative-order deflection at the longer interface, and asymmetry in coupling at the exit interfaces and does not need blocking of transmission by dispersion in the backward illumination case. The Floquet--Bloch mode with left-handed behavior and nearly circular equifrequency dispersion contours is utilized. The outgoing waves may have significantly different spatial distributions for the forward and backward illumination cases, yielding asymmetry in the beaming regime. |
| 23. | Felix Groß, Mateusz Zelent, Ajay Gangwar, Sławomir Mamica, Paweł Gruszecki, Matthias Werner, Gisela Schütz, Markus Weigand, Eberhard J Goering, Christian H Back, Maciej Krawczyk, Joachim Gräfe Phase resolved observation of spin wave modes in antidot lattices Appl. Phys. Lett., 118 (23), pp. 232403, 2021. @article{doi:10.1063/5.0045142, title = {Phase resolved observation of spin wave modes in antidot lattices}, author = {Felix Groß and Mateusz Zelent and Ajay Gangwar and Sławomir Mamica and Paweł Gruszecki and Matthias Werner and Gisela Schütz and Markus Weigand and Eberhard J Goering and Christian H Back and Maciej Krawczyk and Joachim Gräfe}, url = {https://doi.org/10.1063/5.0045142}, doi = {10.1063/5.0045142}, year = {2021}, date = {2021-06-10}, journal = {Appl. Phys. Lett.}, volume = {118}, number = {23}, pages = {232403}, abstract = {Antidot lattices have proven to be a powerful tool for spin wave band structure manipulation. Utilizing time-resolved scanning transmission x-ray microscopy, we are able to experimentally image edge-localized spin wave modes in an antidot lattice with a lateral confinement down to <80nm x 130 nm. At higher frequencies, spin wave dragonfly patterns formed by the demagnetizing structures of the antidot lattice are excited. Evaluating their relative phase with respect to the propagating mode within the antidot channel reveals that the dragonfly modes are not directly excited by the antenna but need the propagating mode as an energy mediator. Furthermore, micromagnetic simulations reveal that additional dispersion branches exist for a tilted external field geometry. These branches correspond to asymmetric spin wave modes that cannot be excited in a non-tilted field geometry due to the symmetry restriction. In addition to the band having a negative slope, these asymmetric modes also cause an unexpected transformation of the band structure, slightly reaching into the otherwise empty bandgap between the low frequency edge modes and the fundamental mode. The presented phase resolved investigation of spin waves is a crucial step for spin wave manipulation in magnonic crystals.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Antidot lattices have proven to be a powerful tool for spin wave band structure manipulation. Utilizing time-resolved scanning transmission x-ray microscopy, we are able to experimentally image edge-localized spin wave modes in an antidot lattice with a lateral confinement down to <80nm x 130 nm. At higher frequencies, spin wave dragonfly patterns formed by the demagnetizing structures of the antidot lattice are excited. Evaluating their relative phase with respect to the propagating mode within the antidot channel reveals that the dragonfly modes are not directly excited by the antenna but need the propagating mode as an energy mediator. Furthermore, micromagnetic simulations reveal that additional dispersion branches exist for a tilted external field geometry. These branches correspond to asymmetric spin wave modes that cannot be excited in a non-tilted field geometry due to the symmetry restriction. In addition to the band having a negative slope, these asymmetric modes also cause an unexpected transformation of the band structure, slightly reaching into the otherwise empty bandgap between the low frequency edge modes and the fundamental mode. The presented phase resolved investigation of spin waves is a crucial step for spin wave manipulation in magnonic crystals. |
| 22. | Iu. V Vetrova, Mateusz Zelent, J Šoltýs, V A Gubanov, A V Sadovnikov, T Šcepka, J Dérer, R Stoklas, V Cambel, M Mruczkiewicz Investigation of self-nucleated skyrmion states in the ferromagnetic/nonmagnetic multilayer dot Appl. Phys. Lett., 118 (21), pp. 212409, 2021. @article{doi:10.1063/5.0045835, title = {Investigation of self-nucleated skyrmion states in the ferromagnetic/nonmagnetic multilayer dot}, author = {Iu. V Vetrova and Mateusz Zelent and J Šoltýs and V A Gubanov and A V Sadovnikov and T Šcepka and J Dérer and R Stoklas and V Cambel and M Mruczkiewicz}, doi = {10.1063/5.0045835}, year = {2021}, date = {2021-05-28}, journal = {Appl. Phys. Lett.}, volume = {118}, number = {21}, pages = {212409}, abstract = {Understanding the stability of magnetic textures in multilayer patterned dots would constitute a significant step toward skyrmion-based applications. Here, we report the observation of skyrmions in patterned nanodots composed of multilayers. We examine the stabilization of various magnetic states such as single-domain states, skyrmion states, horseshoe-like domain structures, and worm-like domain structures in submicrometer dots (diameters 150–525 nm). Dots are fabricated from Pt/Co/Au multilayer structures that exhibit the interfacial Dzyaloshinskii–Moriya interaction and perpendicular magnetic anisotropy. In particular, we show that a stack of six repetitions of Pt/Co/Au layers suffices to stabilize the skyrmion state inside a dot at room temperature. A micromagnetic simulation determines the regime of skyrmion stability. The results reveal a correlation between the magnetic-force microscopy measurements and the micromagnetic simulation. Furthermore, we explain the development of the magnetic state with increasing dot diameter. We envision that nanopatterning of multilayer magnetic films could serve as a versatile way of creating magnetic skyrmion states.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Understanding the stability of magnetic textures in multilayer patterned dots would constitute a significant step toward skyrmion-based applications. Here, we report the observation of skyrmions in patterned nanodots composed of multilayers. We examine the stabilization of various magnetic states such as single-domain states, skyrmion states, horseshoe-like domain structures, and worm-like domain structures in submicrometer dots (diameters 150–525 nm). Dots are fabricated from Pt/Co/Au multilayer structures that exhibit the interfacial Dzyaloshinskii–Moriya interaction and perpendicular magnetic anisotropy. In particular, we show that a stack of six repetitions of Pt/Co/Au layers suffices to stabilize the skyrmion state inside a dot at room temperature. A micromagnetic simulation determines the regime of skyrmion stability. The results reveal a correlation between the magnetic-force microscopy measurements and the micromagnetic simulation. Furthermore, we explain the development of the magnetic state with increasing dot diameter. We envision that nanopatterning of multilayer magnetic films could serve as a versatile way of creating magnetic skyrmion states. |
| 21. | Tomasz Lehmann, Magdalena Wojtków, Ewa Pruszynska-Oszmałek, Paweł Kołodziejski, Celina Pezowicz, Aleksandra Trzaskowska, Sławomir Mielcarek, Mirosław Szybowicz, Ariadna B Nowicka, Marek Nowicki, Ewa Misterska, Ewa Iwańczyk-Skalska, Paweł Jagodziński, Maciej Głowacki Acta of Bioengineering and Biomechanics, 23 (3), pp. 1 -17, 2021. @article{000231402, title = {Trabecular bone remodelling in the femur of C57BL/6J mice treated with diclofenac in combination with treadmill exercise}, author = {Tomasz Lehmann and Magdalena Wojtków and Ewa Pruszynska-Oszmałek and Paweł Kołodziejski and Celina Pezowicz and Aleksandra Trzaskowska and Sławomir Mielcarek and Mirosław Szybowicz and Ariadna B Nowicka and Marek Nowicki and Ewa Misterska and Ewa Iwańczyk-Skalska and Paweł Jagodziński and Maciej Głowacki}, url = {http://www.actabio.pwr.wroc.pl/Vol23No3/41.pdf}, year = {2021}, date = {2021-05-13}, journal = {Acta of Bioengineering and Biomechanics}, volume = {23}, number = {3}, pages = {1 -17}, abstract = {Analgesic treatment with diclofenac deteriorates bone structure and decreases biomechanical properties. This bone loss has been though to be reversed by training. The impact of exercise on bone treated with diclofenac (DF) has reminded elusive. In the present study, we assayed the combined impact of exercises and DF on mouse femur. Methods: The femur samples we obtained from 30 days treated C57BL/6J female mice. The training group ran on a horizontal treadmill at 12 m/min by 30 min a day (5% grade/slope). The group of ten mice treated with DF received the drug subcutaneously every day (5 mg/kg of body weight/day). The combined group ran on the treadmill and obtained DF. After 30 days, we sacrificed mice and studied their femurs using microcomputed tomography (μCT), dynamic mechanical analysis (DMA) and nanoindentation. Results: We observed that treadmill running and DF decreased trabecular bone volume and mineral density. Combined effect of training and DF was not additive. A significant interaction of both parameters suggested protective effect of training on bone loss provoked by DF. The femur cortical bone shell remained untouched by the training and treatment. The training and the DF treatment did not alter the storage modulus E significantly. The unchanged storage modulus would be suggesting on the unaltered bone strength. Conclusions: We concluded that even relatively short time of training with concomitant DF treatment could be protective on trabecular bone. Although viscoelastic properties of the entire femur were not modulated, femur trabecular tissue was thinned by treatment with DF and protected by training.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Analgesic treatment with diclofenac deteriorates bone structure and decreases biomechanical properties. This bone loss has been though to be reversed by training. The impact of exercise on bone treated with diclofenac (DF) has reminded elusive. In the present study, we assayed the combined impact of exercises and DF on mouse femur. Methods: The femur samples we obtained from 30 days treated C57BL/6J female mice. The training group ran on a horizontal treadmill at 12 m/min by 30 min a day (5% grade/slope). The group of ten mice treated with DF received the drug subcutaneously every day (5 mg/kg of body weight/day). The combined group ran on the treadmill and obtained DF. After 30 days, we sacrificed mice and studied their femurs using microcomputed tomography (μCT), dynamic mechanical analysis (DMA) and nanoindentation. Results: We observed that treadmill running and DF decreased trabecular bone volume and mineral density. Combined effect of training and DF was not additive. A significant interaction of both parameters suggested protective effect of training on bone loss provoked by DF. The femur cortical bone shell remained untouched by the training and treatment. The training and the DF treatment did not alter the storage modulus E significantly. The unchanged storage modulus would be suggesting on the unaltered bone strength. Conclusions: We concluded that even relatively short time of training with concomitant DF treatment could be protective on trabecular bone. Although viscoelastic properties of the entire femur were not modulated, femur trabecular tissue was thinned by treatment with DF and protected by training. |
| 20. | Pierre Roberjot, Krzysztof Szulc, Jarosław W. Kłos, Maciej Krawczyk Appl. Phys. Lett., 118 (18), pp. 182406, 2021. @article{doi:10.1063/5.0046001b, title = {Multifunctional operation of the double-layer ferromagnetic structure coupled by a rectangular nanoresonator}, author = {Pierre Roberjot and Krzysztof Szulc and Jarosław W. Kłos and Maciej Krawczyk}, url = {https://doi.org/10.1063/5.0046001}, doi = {10.1063/5.0046001}, year = {2021}, date = {2021-05-05}, journal = {Appl. Phys. Lett.}, volume = {118}, number = {18}, pages = {182406}, abstract = {The use of spin waves as a signal carrier requires developing the functional elements allowing for multiplexing and demultiplexing information coded at different wavelengths. For this purpose, we propose a system of thin ferromagnetic layers dynamically coupled by a rectangular ferromagnetic resonator. We show that single and double, clockwise and counterclockwise, circulating modes of the resonator offer a wide possibility of control of propagating waves. Particularly, at frequency related to the double-clockwise circulating spin-wave mode of the resonator, the spin wave excited in one layer is transferred to the second one where it propagates in the backward direction. Interestingly, the wave excited in the second layer propagates in the forward direction only in that layer. This demonstrates add-drop filtering and circulator functionality. Thus, the proposed system can become an important part of future magnonic technology for signal routing.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The use of spin waves as a signal carrier requires developing the functional elements allowing for multiplexing and demultiplexing information coded at different wavelengths. For this purpose, we propose a system of thin ferromagnetic layers dynamically coupled by a rectangular ferromagnetic resonator. We show that single and double, clockwise and counterclockwise, circulating modes of the resonator offer a wide possibility of control of propagating waves. Particularly, at frequency related to the double-clockwise circulating spin-wave mode of the resonator, the spin wave excited in one layer is transferred to the second one where it propagates in the backward direction. Interestingly, the wave excited in the second layer propagates in the forward direction only in that layer. This demonstrates add-drop filtering and circulator functionality. Thus, the proposed system can become an important part of future magnonic technology for signal routing. |
| 19. | Jan Roik, Karol Bartkiewicz, Antonín Černoch, Karel Lemr Phys. Rev. Applied, 15 , pp. 054006, 2021. @article{Bartkiewicz2021b, title = {Accuracy of Entanglement Detection via Artificial Neural Networks and Human-Designed Entanglement Witnesses}, author = {Jan Roik and Karol Bartkiewicz and Antonín Černoch and Karel Lemr}, url = {https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.15.054006}, doi = {https://doi.org/10.1103/PhysRevApplied.15.054006}, year = {2021}, date = {2021-05-04}, journal = {Phys. Rev. Applied}, volume = {15}, pages = {054006}, abstract = {The detection of entangled states is essential in both fundamental and applied quantum physics. However, this task proves to be challenging, especially for general quantum states. One can execute full state tomography but this method is time demanding, especially in complex systems. Other approaches use entanglement witnesses: these methods tend to be less demanding but lack reliability. Here, we demonstrate that artificial neural networks (ANNs) provide a balance between the two approaches. In this paper, we make a comparison of ANN performance with witness-based methods for random general two-qubit quantum states without any prior information on the states. Furthermore, we apply our approach to a real experimental data set.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The detection of entangled states is essential in both fundamental and applied quantum physics. However, this task proves to be challenging, especially for general quantum states. One can execute full state tomography but this method is time demanding, especially in complex systems. Other approaches use entanglement witnesses: these methods tend to be less demanding but lack reliability. Here, we demonstrate that artificial neural networks (ANNs) provide a balance between the two approaches. In this paper, we make a comparison of ANN performance with witness-based methods for random general two-qubit quantum states without any prior information on the states. Furthermore, we apply our approach to a real experimental data set. |
| 18. | Ryszard Taranko, Kacper Wrześniewski, Bartłomiej Baran, Ireneusz Weymann, Tadeusz Domański Phys. Rev. B, 103 , pp. 165430, 2021. @article{Taranko2021, title = {Transient effects in a double quantum dot sandwiched laterally between superconducting and metallic leads}, author = {Ryszard Taranko and Kacper Wrześniewski and Bartłomiej Baran and Ireneusz Weymann and Tadeusz Domański}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.165430}, doi = {10.1103/PhysRevB.103.165430}, year = {2021}, date = {2021-04-29}, journal = {Phys. Rev. B}, volume = {103}, pages = {165430}, abstract = {We study the transient phenomena appearing in a subgap region of the double quantum dot coupled in series between the superconducting and normal metallic leads, focusing on the development of the superconducting proximity effect. For the uncorrelated nanostructure we derive explicit expressions of the time-dependent occupancies in both quantum dots, charge currents, and electron pairing induced on individual dots and between them. We show that the initial configurations substantially affect the dynamical processes, in which the in-gap bound states emerge upon coupling the double quantum dot to the superconducting reservoir. In particular, the superconducting proximity effect would be temporarily blocked whenever the quantum dots are initially singly occupied. Such triplet/Andreev blockade has been recently reported experimentally for double quantum dots embedded in the Josephson [Bouman et al., Phys. Rev. B 102, 220505 (2020)] and Andreev [Zhang et al., arXiv:2102.03283 (2021)] junctions. We also address the role of correlation effects within the lowest-order decoupling scheme and by the time-dependent numerical renormalization group calculations. Competition of the repulsive Coulomb interactions with the superconducting proximity effect leads to renormalization of the in-gap quasiparticles, speeding up the quantum oscillations and narrowing a region of transient phenomena, whereas the dynamical Andreev blockade is well pronounced in the weak interdot coupling limit. We propose feasible methods for detecting the characteristic timescales that could be observable by the Andreev spectroscopy.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We study the transient phenomena appearing in a subgap region of the double quantum dot coupled in series between the superconducting and normal metallic leads, focusing on the development of the superconducting proximity effect. For the uncorrelated nanostructure we derive explicit expressions of the time-dependent occupancies in both quantum dots, charge currents, and electron pairing induced on individual dots and between them. We show that the initial configurations substantially affect the dynamical processes, in which the in-gap bound states emerge upon coupling the double quantum dot to the superconducting reservoir. In particular, the superconducting proximity effect would be temporarily blocked whenever the quantum dots are initially singly occupied. Such triplet/Andreev blockade has been recently reported experimentally for double quantum dots embedded in the Josephson [Bouman et al., Phys. Rev. B 102, 220505 (2020)] and Andreev [Zhang et al., arXiv:2102.03283 (2021)] junctions. We also address the role of correlation effects within the lowest-order decoupling scheme and by the time-dependent numerical renormalization group calculations. Competition of the repulsive Coulomb interactions with the superconducting proximity effect leads to renormalization of the in-gap quasiparticles, speeding up the quantum oscillations and narrowing a region of transient phenomena, whereas the dynamical Andreev blockade is well pronounced in the weak interdot coupling limit. We propose feasible methods for detecting the characteristic timescales that could be observable by the Andreev spectroscopy. |
| 17. | Anand Manaparambil, Ireneusz Weymann Spin Seebeck effect of correlated magnetic molecules Sci. Rep., 11 (9192), pp. 1-15, 2021. @article{Man2021April, title = {Spin Seebeck effect of correlated magnetic molecules}, author = {Anand Manaparambil and Ireneusz Weymann}, url = {https://www.nature.com/articles/s41598-021-88373-7}, doi = {10.1038/s41598-021-88373-7}, year = {2021}, date = {2021-04-28}, journal = {Sci. Rep.}, volume = {11}, number = {9192}, pages = {1-15}, abstract = {In this paper we investigate the spin-resolved thermoelectric properties of strongly correlated molecular junctions in the linear response regime. The magnetic molecule is modeled by a single orbital level to which the molecular core spin is attached by an exchange interaction. Using the numerical renormalization group method we analyze the behavior of the (spin) Seebeck effect, heat conductance and figure of merit for different model parameters of the molecule. We show that the thermopower strongly depends on the strength and type of the exchange interaction as well as the molecule’s magnetic anisotropy. When the molecule is coupled to ferromagnetic leads, the thermoelectric properties reveal an interplay between the spin-resolved tunneling processes and intrinsic magnetic properties of the molecule. Moreover, in the case of finite spin accumulation in the leads, the system exhibits the spin Seebeck effect. We demonstrate that a considerable spin Seebeck effect can develop when the molecule exhibits an easy-plane magnetic anisotropy, while the sign of the spin thermopower depends on the type and magnitude of the molecule’s exchange interaction.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper we investigate the spin-resolved thermoelectric properties of strongly correlated molecular junctions in the linear response regime. The magnetic molecule is modeled by a single orbital level to which the molecular core spin is attached by an exchange interaction. Using the numerical renormalization group method we analyze the behavior of the (spin) Seebeck effect, heat conductance and figure of merit for different model parameters of the molecule. We show that the thermopower strongly depends on the strength and type of the exchange interaction as well as the molecule’s magnetic anisotropy. When the molecule is coupled to ferromagnetic leads, the thermoelectric properties reveal an interplay between the spin-resolved tunneling processes and intrinsic magnetic properties of the molecule. Moreover, in the case of finite spin accumulation in the leads, the system exhibits the spin Seebeck effect. We demonstrate that a considerable spin Seebeck effect can develop when the molecule exhibits an easy-plane magnetic anisotropy, while the sign of the spin thermopower depends on the type and magnitude of the molecule’s exchange interaction. |
| 16. | Ataollah Kalantari Osgouei, Hodjat Hajian, Andriy E. Serebryannikov, Ekmel Ozbay J. Phys. D: Appl. Phys., 54 (27), pp. 275102, 2021. @article{Osgouei_2021, title = {Hybrid indium tin oxide-Au metamaterial as a multiband bi-functional light absorber in the visible and near-infrared ranges}, author = {Ataollah Kalantari Osgouei and Hodjat Hajian and Andriy E. Serebryannikov and Ekmel Ozbay}, url = {https://doi.org/10.1088/1361-6463/abf579}, doi = {10.1088/1361-6463/abf579}, year = {2021}, date = {2021-04-23}, journal = {J. Phys. D: Appl. Phys.}, volume = {54}, number = {27}, pages = {275102}, publisher = {IOP Publishing}, abstract = {Metamaterial nearly perfect light absorbers (MPAs) with dual-narrowband functionality—that absorb light in two narrowband adjacent wavelength regions—have attracted considerable attention due to their intriguing applications, such as sensing, photovoltaic, and thermal emission. Here, we propose a multi-band MPA with two narrowband absorption responses that are centered on the visible and near-infrared (NIR) wavelengths (773 nm and 900 nm, respectively) and a broadband absorptive characteristic in another window in the NIR region (ranging from 1530 nm to 2700 nm with a bandwidth of 1170 nm). The MPA comprises a periodic array of self-aligned hybrid indium tin oxide (ITO)-Au split-ring-resonators that are separated from an optically thick bottom reflector with a SiO2 layer. Based on numerical calculations, which are accompanied with a semi-analytical examination, we find that the dual narrowband and broadband responses are attributed to the hybridization of the optical responses of gold as a plasmonic material with the ones of ITO. Note that ITO acts as a low-loss dielectric in the visible range and a lossy plasmonic material in the NIR region. Moreover, due to the applied symmetry in the unit cell of the metamaterial, the proposed MPA represents polarization insensitive and omnidirectional absorptive features. The proposed metastructure can find potential applications in selective thermophotovoltaic devices, thermal emitters, and sensors.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Metamaterial nearly perfect light absorbers (MPAs) with dual-narrowband functionality—that absorb light in two narrowband adjacent wavelength regions—have attracted considerable attention due to their intriguing applications, such as sensing, photovoltaic, and thermal emission. Here, we propose a multi-band MPA with two narrowband absorption responses that are centered on the visible and near-infrared (NIR) wavelengths (773 nm and 900 nm, respectively) and a broadband absorptive characteristic in another window in the NIR region (ranging from 1530 nm to 2700 nm with a bandwidth of 1170 nm). The MPA comprises a periodic array of self-aligned hybrid indium tin oxide (ITO)-Au split-ring-resonators that are separated from an optically thick bottom reflector with a SiO2 layer. Based on numerical calculations, which are accompanied with a semi-analytical examination, we find that the dual narrowband and broadband responses are attributed to the hybridization of the optical responses of gold as a plasmonic material with the ones of ITO. Note that ITO acts as a low-loss dielectric in the visible range and a lossy plasmonic material in the NIR region. Moreover, due to the applied symmetry in the unit cell of the metamaterial, the proposed MPA represents polarization insensitive and omnidirectional absorptive features. The proposed metastructure can find potential applications in selective thermophotovoltaic devices, thermal emitters, and sensors. |
| 15. | Kacper Wrześniewski, Bartłomiej Baran, Ryszard Taranko, Tadeusz Domański, Ireneusz Weymann Phys. Rev. B, 103 , pp. 155420, 2021. @article{Wrzesniewski2021April, title = {Quench dynamics of a correlated quantum dot sandwiched between normal-metal and superconducting leads}, author = {Kacper Wrześniewski and Bartłomiej Baran and Ryszard Taranko and Tadeusz Domański and Ireneusz Weymann}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.155420}, doi = {https://doi.org/10.1103/PhysRevB.103.155420}, year = {2021}, date = {2021-04-22}, journal = {Phys. Rev. B}, volume = {103}, pages = {155420}, abstract = {Quantum system abruptly driven from its stationary phase can reveal nontrivial dynamics upon approaching a new final state. We investigate here such dynamics for a correlated quantum dot sandwiched between the metallic and superconducting leads, considering two types of quenches feasible experimentally. The first one is related to a sudden change of the coupling between the dot and the superconducting lead, while the other one is associated with an abrupt shift of the quantum dot energy level. Using the time-dependent numerical renormalization group method, we examine and quantify the interplay between the proximity induced electron pairing with correlations caused by the on-dot Coulomb repulsion. We determine and discuss the time-dependent charge occupancy, on-dot pair correlation, transient currents, and analyze the evolution of the subgap quasiparticles, which could be empirically observed in the tunneling conductance. To get some insight into the dynamics of a biased junction, we make use of a mean-field approximation. We reveal the signatures of the time-dependent 0-π transition and demonstrate that the evolution of local observables exhibits damped quantum oscillations with frequencies given by the energies of Andreev bound states}, keywords = {}, pubstate = {published}, tppubtype = {article} } Quantum system abruptly driven from its stationary phase can reveal nontrivial dynamics upon approaching a new final state. We investigate here such dynamics for a correlated quantum dot sandwiched between the metallic and superconducting leads, considering two types of quenches feasible experimentally. The first one is related to a sudden change of the coupling between the dot and the superconducting lead, while the other one is associated with an abrupt shift of the quantum dot energy level. Using the time-dependent numerical renormalization group method, we examine and quantify the interplay between the proximity induced electron pairing with correlations caused by the on-dot Coulomb repulsion. We determine and discuss the time-dependent charge occupancy, on-dot pair correlation, transient currents, and analyze the evolution of the subgap quasiparticles, which could be empirically observed in the tunneling conductance. To get some insight into the dynamics of a biased junction, we make use of a mean-field approximation. We reveal the signatures of the time-dependent 0-π transition and demonstrate that the evolution of local observables exhibits damped quantum oscillations with frequencies given by the energies of Andreev bound states |
| 14. | Krzysztof Szulc, Simon Mendisch, Michał Mruczkiewicz, Francesca Casoli, Markus Becherer, Gianluca Gubbiotti Nonreciprocal spin-wave dynamics in Pt/Co/W/Co/Pt multilayers Phys. Rev. B, 103 , pp. 134404, 2021. @article{PhysRevB.103.134404, title = {Nonreciprocal spin-wave dynamics in Pt/Co/W/Co/Pt multilayers}, author = {Krzysztof Szulc and Simon Mendisch and Michał Mruczkiewicz and Francesca Casoli and Markus Becherer and Gianluca Gubbiotti}, url = {https://link.aps.org/doi/10.1103/PhysRevB.103.134404}, doi = {10.1103/PhysRevB.103.134404}, year = {2021}, date = {2021-04-01}, journal = {Phys. Rev. B}, volume = {103}, pages = {134404}, publisher = {American Physical Society}, abstract = {We present a detailed study of the spin-wave dynamics in single Pt/Co/W and double Pt/Co/W/Co/Pt ferromagnetic layer systems. The dispersion of spin waves was measured by wave-vector-resolved Brillouin light scattering spectroscopy while the in-plane and out-of-plane magnetization curves were measured by alternating gradient field magnetometry. The interfacial Dzyaloshinskii-Moriya interaction induced nonreciprocal dispersion relation was demonstrated for both single and double ferromagnetic layers and explicated by numerical simulations and theoretical formulas. The results indicate the crucial role of the order of layers deposition on the magnetic parameters. A significant difference between the perpendicular magnetic anisotropy constant in double ferromagnetic layer systems conduces to the decline of the interlayer interactions and different dispersion relations for the spin-wave modes. Our study provides a significant contribution to the realization of the multifunctional nonreciprocal magnonic devices based on ultrathin ferromagnetic/heavy-metal layer systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a detailed study of the spin-wave dynamics in single Pt/Co/W and double Pt/Co/W/Co/Pt ferromagnetic layer systems. The dispersion of spin waves was measured by wave-vector-resolved Brillouin light scattering spectroscopy while the in-plane and out-of-plane magnetization curves were measured by alternating gradient field magnetometry. The interfacial Dzyaloshinskii-Moriya interaction induced nonreciprocal dispersion relation was demonstrated for both single and double ferromagnetic layers and explicated by numerical simulations and theoretical formulas. The results indicate the crucial role of the order of layers deposition on the magnetic parameters. A significant difference between the perpendicular magnetic anisotropy constant in double ferromagnetic layer systems conduces to the decline of the interlayer interactions and different dispersion relations for the spin-wave modes. Our study provides a significant contribution to the realization of the multifunctional nonreciprocal magnonic devices based on ultrathin ferromagnetic/heavy-metal layer systems. |
| 13. | Kacper Wrześniewski, Ireneusz Weymann Magnetization dynamics in a Majorana-wire–quantum-dot setup Phys. Rev. B, 103 , pp. 125413, 2021. @article{Wrzesniewski2021Mar, title = {Magnetization dynamics in a Majorana-wire–quantum-dot setup}, author = {Kacper Wrześniewski and Ireneusz Weymann}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.125413}, doi = {https://doi.org/10.1103/PhysRevB.103.125413}, year = {2021}, date = {2021-03-11}, journal = {Phys. Rev. B}, volume = {103}, pages = {125413}, abstract = {We theoretically study the quench dynamics of the local magnetization in a hybrid Majorana-wire–quantum-dot system coupled to external leads. In order to thoroughly understand the origin of the dot magnetization dynamics, we consider either normal metal or ferromagnetic electrodes. In the first case, the magnetization arises exclusively from the proximity to the topological superconductor hosting Majorana zero-energy modes and the associated development of an induced exchange field. We predict a nonmonotonic dependence of the dot's magnetization in the odd-occupation regime and show that the dynamics is governed by the magnitude of the coupling to Majorana wire. However, when the system is coupled to ferromagnetic leads, the ferromagnet and Majorana contributions to the effective exchange field are competing with each other and reveal a nontrivial dynamical behavior. As a result, the time-dependent magnetization can undergo multiple sign changes preceding the relaxation to a new thermal value. We also identify the transport regime, where fine tuning of the coupling to Majorana wire within a narrow range allows one to manipulate the magnetic state of the system. The effect of spin polarization of the leads and influence of the finite overlap between the Majorana edge modes are also examined. Moreover, we analyze the quench in the energy of the quantum dot orbital level and demonstrate that the rather straightforward charge dynamics can disguise nontrivial time evolution of the magnetization. Finally, we compare predicted dynamics with results obtained for quantum dot coupled to spin-polarized fermionic bound state instead of Majorana zero-energy mode.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We theoretically study the quench dynamics of the local magnetization in a hybrid Majorana-wire–quantum-dot system coupled to external leads. In order to thoroughly understand the origin of the dot magnetization dynamics, we consider either normal metal or ferromagnetic electrodes. In the first case, the magnetization arises exclusively from the proximity to the topological superconductor hosting Majorana zero-energy modes and the associated development of an induced exchange field. We predict a nonmonotonic dependence of the dot's magnetization in the odd-occupation regime and show that the dynamics is governed by the magnitude of the coupling to Majorana wire. However, when the system is coupled to ferromagnetic leads, the ferromagnet and Majorana contributions to the effective exchange field are competing with each other and reveal a nontrivial dynamical behavior. As a result, the time-dependent magnetization can undergo multiple sign changes preceding the relaxation to a new thermal value. We also identify the transport regime, where fine tuning of the coupling to Majorana wire within a narrow range allows one to manipulate the magnetic state of the system. The effect of spin polarization of the leads and influence of the finite overlap between the Majorana edge modes are also examined. Moreover, we analyze the quench in the energy of the quantum dot orbital level and demonstrate that the rather straightforward charge dynamics can disguise nontrivial time evolution of the magnetization. Finally, we compare predicted dynamics with results obtained for quantum dot coupled to spin-polarized fermionic bound state instead of Majorana zero-energy mode. |
| 12. | Krzysztof Sobucki, Wojciech Śmigaj, Justyna Rychły, Maciej Krawczyk, Paweł Gruszecki Sci. Rep., 11 (1), pp. 4428, 2021, ISSN: 2045-2322. @article{sobucki_resonant_2021, title = {Resonant subwavelength control of the phase of spin waves reflected from a Gires–Tournois interferometer}, author = {Krzysztof Sobucki and Wojciech Śmigaj and Justyna Rychły and Maciej Krawczyk and Paweł Gruszecki}, url = {https://www.nature.com/articles/s41598-021-83307-9}, doi = {10.1038/s41598-021-83307-9}, issn = {2045-2322}, year = {2021}, date = {2021-02-24}, urldate = {2021-02-25}, journal = {Sci. Rep.}, volume = {11}, number = {1}, pages = {4428}, abstract = {Subwavelength resonant elements are essential building blocks of metamaterials and metasurfaces, which have revolutionized photonics. Despite similarities between different wave phenomena, other types of interactions can make subwavelength coupling significantly distinct; its investigation in their context is therefore of interest both from the physics and applications perspective. In this work, we demonstrate a fully magnonic Gires–Tournois interferometer based on a subwavelength resonator made of a narrow ferromagnetic stripe lying above the edge of a ferromagnetic film. The bilayer formed by the stripe and the film underneath supports two propagative spin-wave modes, one strongly coupled with spin waves propagating in the rest of the film and another almost completely reflected at the ends of the bilayer. When the Fabry–Perot resonance conditions for this mode are satisfied, the weak coupling between both modes is sufficient to achieve high sensitivity of the phase of waves reflected from the resonator to the stripe width and, more interestingly, also to the stripe-film separation. Such spin-wave phase manipulation capabilities are a prerequisite for the design of spin-wave metasurfaces and may stimulate development of magnonic logic devices and sensors detecting magnetic nanoparticles.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Subwavelength resonant elements are essential building blocks of metamaterials and metasurfaces, which have revolutionized photonics. Despite similarities between different wave phenomena, other types of interactions can make subwavelength coupling significantly distinct; its investigation in their context is therefore of interest both from the physics and applications perspective. In this work, we demonstrate a fully magnonic Gires–Tournois interferometer based on a subwavelength resonator made of a narrow ferromagnetic stripe lying above the edge of a ferromagnetic film. The bilayer formed by the stripe and the film underneath supports two propagative spin-wave modes, one strongly coupled with spin waves propagating in the rest of the film and another almost completely reflected at the ends of the bilayer. When the Fabry–Perot resonance conditions for this mode are satisfied, the weak coupling between both modes is sufficient to achieve high sensitivity of the phase of waves reflected from the resonator to the stripe width and, more interestingly, also to the stripe-film separation. Such spin-wave phase manipulation capabilities are a prerequisite for the design of spin-wave metasurfaces and may stimulate development of magnonic logic devices and sensors detecting magnetic nanoparticles. |
| 11. | Paweł Gruszecki, Igor L. Lyubchanskii, Konstantin Y Guslienko, Maciej Krawczyk Appl. Phys. Lett., 118 (6), pp. 062408, 2021. @article{doi:10.1063/5.0041030, title = {Local non-linear excitation of sub-100 nm bulk-type spin waves by edge-localized spin waves in magnetic films}, author = {Paweł Gruszecki and Igor L. Lyubchanskii and Konstantin Y Guslienko and Maciej Krawczyk}, doi = {10.1063/5.0041030}, year = {2021}, date = {2021-02-11}, journal = {Appl. Phys. Lett.}, volume = {118}, number = {6}, pages = {062408}, abstract = {The excitation of high-frequency short-wavelength spin waves is a challenge limiting the application of these propagating magnetization disturbances in information processing systems. We propose a method of local excitation of the high-frequency spin waves using the non-linear nature of magnetization dynamics. We demonstrate with numeric simulations that an edge-localized spin wave can be used to excite plane waves propagating obliquely from the film's edge at a doubled frequency and over twice shorter in wavelength. The excitation mechanism is a direct result of the ellipticity of the magnetic moment precession that is related to the edge-mode propagation. As a consequence, the magnetization component tangential to the equilibrium orientation oscillates with doubled temporal and spatial frequencies, which leads to efficient excitation of the plane spin waves. The threshold-less non-linear process of short-wavelength spin-wave excitation proposed in our study is promising for integration with an inductive or point-like spin-torque source of edge spin waves. The research leading to these results received funding from the National Science Centre of Poland, Project No. 2019/35/D/ST3/03729. I.L.L. acknowledges support from a COST action under Project No. CA17123 MAGNETOFON. K.Y.G. acknowledges support from IKERBASQUE (the Basque Foundation for Science) and from the Spanish Ministerio de Ciencia, Innovacion y Universidades Grant No. PID2019-108075RB-C33/AEI/10.13039/501100011033. The simulations were partially performed at the Poznan Supercomputing and Networking Center (Grant No. 398).}, keywords = {}, pubstate = {published}, tppubtype = {article} } The excitation of high-frequency short-wavelength spin waves is a challenge limiting the application of these propagating magnetization disturbances in information processing systems. We propose a method of local excitation of the high-frequency spin waves using the non-linear nature of magnetization dynamics. We demonstrate with numeric simulations that an edge-localized spin wave can be used to excite plane waves propagating obliquely from the film's edge at a doubled frequency and over twice shorter in wavelength. The excitation mechanism is a direct result of the ellipticity of the magnetic moment precession that is related to the edge-mode propagation. As a consequence, the magnetization component tangential to the equilibrium orientation oscillates with doubled temporal and spatial frequencies, which leads to efficient excitation of the plane spin waves. The threshold-less non-linear process of short-wavelength spin-wave excitation proposed in our study is promising for integration with an inductive or point-like spin-torque source of edge spin waves. The research leading to these results received funding from the National Science Centre of Poland, Project No. 2019/35/D/ST3/03729. I.L.L. acknowledges support from a COST action under Project No. CA17123 MAGNETOFON. K.Y.G. acknowledges support from IKERBASQUE (the Basque Foundation for Science) and from the Spanish Ministerio de Ciencia, Innovacion y Universidades Grant No. PID2019-108075RB-C33/AEI/10.13039/501100011033. The simulations were partially performed at the Poznan Supercomputing and Networking Center (Grant No. 398). |
| 10. | Jarosław W. Kłos, Igor L. Lyubchanskii, Maciej Krawczyk, Paweł Gruszecki, Szymon Mieszczak, Justyna Rychły, Yuliya S. Dadoenkova, Nataliya N. Dadoenkova Magnonics and Confinement of Light in Photonic–Magnonic Crystals, in Optomagnonic Structures Almpanis, Evangelos (Ed.): Chapter 2, pp. 79–134, World Scientific Publishing, Singapure, 2021, ISBN: 978-981-122-005-0. @inbook{opto-mag, title = {Magnonics and Confinement of Light in Photonic–Magnonic Crystals, in Optomagnonic Structures}, author = {Jarosław W. Kłos and Igor L. Lyubchanskii and Maciej Krawczyk and Paweł Gruszecki and Szymon Mieszczak and Justyna Rychły and Yuliya S. Dadoenkova and Nataliya N. Dadoenkova}, editor = {Evangelos Almpanis}, doi = {10.1142/9789811220050_0002}, isbn = {978-981-122-005-0}, year = {2021}, date = {2021-02-08}, pages = {79–134}, publisher = {World Scientific Publishing}, address = {Singapure}, chapter = {2}, abstract = {We discuss the spin-wave confinement in the magnetic components of magnetophotonic structures. In the initial sections of the chapter, we describe the principles of magnetization dynamics, including both the exchange and dipolar interactions. We showed that the spin-wave spectrum in confined geometry is determined not only by the spatial constraints but is also strongly influenced by non-local demagnetizing effects. In addition, we analyze the localization of light in the regions of spin-wave confinement, which can strengthen the magneto–optical interaction. Such enhancement can be potentially realized in photonic–magnonic crystals, where the light localization in magnetic components of the structure results from the periodicity and the spin waves co-exist with electromagnetic waves. The final sections are devoted to the Faraday effect and Goos–Hänchen effect in photonic–magnonic crystals.}, keywords = {}, pubstate = {published}, tppubtype = {inbook} } We discuss the spin-wave confinement in the magnetic components of magnetophotonic structures. In the initial sections of the chapter, we describe the principles of magnetization dynamics, including both the exchange and dipolar interactions. We showed that the spin-wave spectrum in confined geometry is determined not only by the spatial constraints but is also strongly influenced by non-local demagnetizing effects. In addition, we analyze the localization of light in the regions of spin-wave confinement, which can strengthen the magneto–optical interaction. Such enhancement can be potentially realized in photonic–magnonic crystals, where the light localization in magnetic components of the structure results from the periodicity and the spin waves co-exist with electromagnetic waves. The final sections are devoted to the Faraday effect and Goos–Hänchen effect in photonic–magnonic crystals. |
| 9. | Nick Träger, Paweł Gruszecki, Filip Lisiecki, Felix Groß, Johannes Förster, Markus Weigand, Hubert Głowiński, Piotr Kuświk, Janusz Dubowik, Gisela Schütz, Maciej Krawczyk, Joachim Gräfe Real-Space Observation of Magnon Interaction with Driven Space-Time Crystals Phys. Rev. Lett., 126 , pp. 057201, 2021. @article{PhysRevLett.126.057201, title = {Real-Space Observation of Magnon Interaction with Driven Space-Time Crystals}, author = {Nick Träger and Paweł Gruszecki and Filip Lisiecki and Felix Groß and Johannes Förster and Markus Weigand and Hubert Głowiński and Piotr Kuświk and Janusz Dubowik and Gisela Schütz and Maciej Krawczyk and Joachim Gräfe}, url = {https://doi.org/10.1103/PhysRevLett.126.057201}, doi = {10.1103/PhysRevLett.126.057201}, year = {2021}, date = {2021-02-03}, journal = {Phys. Rev. Lett.}, volume = {126}, pages = {057201}, abstract = {The concept of space-time crystals (STC), i.e., translational symmetry breaking in time and space, was recently proposed and experimentally demonstrated for quantum systems. Here, we transfer this concept to magnons and experimentally demonstrate a driven STC at room temperature. The STC is realized by strong homogeneous microwave pumping of a micron-sized permalloy (Py) stripe and is directly imaged by scanning transmission x-ray microscopy (STXM). For a fundamental understanding of the formation of the STC, micromagnetic simulations are carefully adapted to model the experimental findings. Beyond the mere generation of a STC, we observe the formation of a magnonic band structure due to back folding of modes at the STC’s Brillouin zone boundaries. We show interactions of magnons with the STC that appear as lattice scattering, which results in the generation of ultrashort spin waves (SW) down to 100-nm wavelengths that cannot be described by classical dispersion relations for linear SW excitation. We expect that room-temperature STCs will be useful to investigate nonlinear wave physics, as they can be easily generated and manipulated to control their spatial and temporal band structures.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The concept of space-time crystals (STC), i.e., translational symmetry breaking in time and space, was recently proposed and experimentally demonstrated for quantum systems. Here, we transfer this concept to magnons and experimentally demonstrate a driven STC at room temperature. The STC is realized by strong homogeneous microwave pumping of a micron-sized permalloy (Py) stripe and is directly imaged by scanning transmission x-ray microscopy (STXM). For a fundamental understanding of the formation of the STC, micromagnetic simulations are carefully adapted to model the experimental findings. Beyond the mere generation of a STC, we observe the formation of a magnonic band structure due to back folding of modes at the STC’s Brillouin zone boundaries. We show interactions of magnons with the STC that appear as lattice scattering, which results in the generation of ultrashort spin waves (SW) down to 100-nm wavelengths that cannot be described by classical dispersion relations for linear SW excitation. We expect that room-temperature STCs will be useful to investigate nonlinear wave physics, as they can be easily generated and manipulated to control their spatial and temporal band structures. |
| 8. | Nick Träger, Filip Lisiecki, Robert Lawitzki, Markus Weigand, Hubert Głowiński, Gisela Schütz, Guido Schmitz, Piotr Kuświk, Maciej Krawczyk, Joachim Gräfe, Paweł Gruszecki Competing spin wave emission mechanisms revealed by time-resolved x-ray microscopy Phys. Rev. B, 103 , pp. 014430, 2021. @article{PhysRevB.103.014430, title = {Competing spin wave emission mechanisms revealed by time-resolved x-ray microscopy}, author = {Nick Träger and Filip Lisiecki and Robert Lawitzki and Markus Weigand and Hubert Głowiński and Gisela Schütz and Guido Schmitz and Piotr Kuświk and Maciej Krawczyk and Joachim Gräfe and Paweł Gruszecki}, url = {https://link.aps.org/doi/10.1103/PhysRevB.103.014430}, doi = {10.1103/PhysRevB.103.014430}, year = {2021}, date = {2021-01-19}, journal = {Phys. Rev. B}, volume = {103}, pages = {014430}, publisher = {American Physical Society}, abstract = {Spin wave emission and propagation in magnonic waveguides represent a highly promising alternative for beyond-CMOS computing. It is therefore all the more important to fully understand the underlying physics of the emission process. Here, we use time-resolved scanning transmission x-ray microscopy to directly image the formation process of the globally excited local emission of spin waves in a permalloy waveguide at the nanoscale. Thereby, we observe spin wave emission from the corner of the waveguide as well as from a local oscillation of a domain-wall-like structure within the waveguide. Additionally, an isofrequency contour analysis is used to fully explain the origin of quasicylindrical spin wave excitation from the corner and its concurrent nonreflection and nonrefraction at the domain interface. This study is complemented by micromagnetic simulations which perfectly fit the experimental findings. Thus, we clarify the fundamental question of the emission mechanisms in magnonic waveguides which lay the basis for future magnonic operations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Spin wave emission and propagation in magnonic waveguides represent a highly promising alternative for beyond-CMOS computing. It is therefore all the more important to fully understand the underlying physics of the emission process. Here, we use time-resolved scanning transmission x-ray microscopy to directly image the formation process of the globally excited local emission of spin waves in a permalloy waveguide at the nanoscale. Thereby, we observe spin wave emission from the corner of the waveguide as well as from a local oscillation of a domain-wall-like structure within the waveguide. Additionally, an isofrequency contour analysis is used to fully explain the origin of quasicylindrical spin wave excitation from the corner and its concurrent nonreflection and nonrefraction at the domain interface. This study is complemented by micromagnetic simulations which perfectly fit the experimental findings. Thus, we clarify the fundamental question of the emission mechanisms in magnonic waveguides which lay the basis for future magnonic operations. |
| 7. | Ataollah Kalantari Osgouei, Hodjat Hajian, Bahram Khalichi, Andriy E. Serebryannikov, Amir Ghobadi, Ekmel Ozbay Active Tuning from Narrowband to Broadband Absorbers Using a Sub-wavelength VO2 Embedded Layer Plasmonics, 2021, ISSN: 1557-1963. @article{kalantari_osgouei_active_2021, title = {Active Tuning from Narrowband to Broadband Absorbers Using a Sub-wavelength VO2 Embedded Layer}, author = {Ataollah Kalantari Osgouei and Hodjat Hajian and Bahram Khalichi and Andriy E. Serebryannikov and Amir Ghobadi and Ekmel Ozbay}, url = {https://doi.org/10.1007/s11468-020-01370-w}, doi = {10.1007/s11468-020-01370-w}, issn = {1557-1963}, year = {2021}, date = {2021-01-18}, urldate = {2021-06-11}, journal = {Plasmonics}, abstract = {Metamaterial perfect absorbers (MPAs) with dynamic thermal tuning features are able to control the absorption performance of the resonances, providing diverse applications spanning from optical switches and filters to modulators. In this paper, we propose an MPA with diverse functionalities enabled by vanadium dioxide (VO2) embedded in a metal-dielectric plasmonic structure. For the initial design purpose, a silicon (Si) nanograting on a silver (Ag) mirror is proposed to have multiple resonant responses in the near infrared (NIR) region. Then, the insertion of a thin VO2 layer at the right position enables the design to act as an on/off switch and resonance tuner. In the insulator phase of VO2, in which the permittivity data of VO2 is similar to that of Si, a double strong resonant behavior is achieved within the NIR region. By increasing the temperature, the state of VO2 transforms from insulator to metallic so that the absorption bands turn into three distinct resonant peaks with close spectral positions. Upon this transformation, a new resonance emerges and the existing resonance features experience blue/red shifts in the spectral domain. The superposition of these peaks makes the overall absorption bandwidth broad. Although Si has a small thermo-optic coefficient, owing to strong light confinement in the ultrasmall gaps, a substantial tuning can be achieved within the Si nanogratings. Therefore, the proposed hybrid design can provide multi-resonance tunable features to cover a broad range and can be a promising strategy for the design of linearly thermal-tunable and broadband MPAs. Owing to the proposed double tuning feature, the resonance wavelengths exhibits great sensitivity to temperature, covering a broad wavelength range$$.$$Overall, the proposed design strategy demonstrates diverse functionalities enabled by the integration of a thin VO2 layer with plasmonic absorbers.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Metamaterial perfect absorbers (MPAs) with dynamic thermal tuning features are able to control the absorption performance of the resonances, providing diverse applications spanning from optical switches and filters to modulators. In this paper, we propose an MPA with diverse functionalities enabled by vanadium dioxide (VO2) embedded in a metal-dielectric plasmonic structure. For the initial design purpose, a silicon (Si) nanograting on a silver (Ag) mirror is proposed to have multiple resonant responses in the near infrared (NIR) region. Then, the insertion of a thin VO2 layer at the right position enables the design to act as an on/off switch and resonance tuner. In the insulator phase of VO2, in which the permittivity data of VO2 is similar to that of Si, a double strong resonant behavior is achieved within the NIR region. By increasing the temperature, the state of VO2 transforms from insulator to metallic so that the absorption bands turn into three distinct resonant peaks with close spectral positions. Upon this transformation, a new resonance emerges and the existing resonance features experience blue/red shifts in the spectral domain. The superposition of these peaks makes the overall absorption bandwidth broad. Although Si has a small thermo-optic coefficient, owing to strong light confinement in the ultrasmall gaps, a substantial tuning can be achieved within the Si nanogratings. Therefore, the proposed hybrid design can provide multi-resonance tunable features to cover a broad range and can be a promising strategy for the design of linearly thermal-tunable and broadband MPAs. Owing to the proposed double tuning feature, the resonance wavelengths exhibits great sensitivity to temperature, covering a broad wavelength range$$.$$Overall, the proposed design strategy demonstrates diverse functionalities enabled by the integration of a thin VO2 layer with plasmonic absorbers. |
| 6. | V.V. Bogdanov, R.V. Vovk, S.V. Dukarov, M.V. Klislitsa, S.I. Petrushenko, V.N. Sukhov, G.Ya. Khadzhai, Y.L. Goulatis, S.R. Vovk, E.S. Gevorkyan, A. Feher, P. Kollar, J. Fuzer, Jolanta Natalia Latosińska Electron Microscopic Study of Interdiffusion in Equiatomic Fe-Ni Composite Acta Physica Polonica A, 139 (1), pp. 62, 2021. @article{Bogdanov2021, title = {Electron Microscopic Study of Interdiffusion in Equiatomic Fe-Ni Composite}, author = {V.V. Bogdanov and R.V. Vovk and S.V. Dukarov and M.V. Klislitsa and S.I. Petrushenko and V.N. Sukhov and G.Ya. Khadzhai and Y.L. Goulatis and S.R. Vovk and E.S. Gevorkyan and A. Feher and P. Kollar and J. Fuzer and Jolanta Natalia Latosińska}, doi = {10.12693/APhysPolA.139.62}, year = {2021}, date = {2021-01-15}, journal = {Acta Physica Polonica A}, volume = {139}, number = {1}, pages = {62}, abstract = {The paper presents a study of interdiffusion processes in a binary Fe-Ni system (obtained by electroconsolidation of nickel and iron powders) by X-ray energy dispersive spectroscopy. Well-separated regions of almost pure iron and nickel have been discovered. The content of nickel, estimated from the concentration dependence of the interdiffusion coefficient, which determines the kinetics of the homogenization process of the electroconsolidated Fe-Ni composite sample, was ~70 at.%. The value of the interdiffusion coefficient of the electroconsolidated Fe-Ni composite is significantly higher than that of the alloy of similar composition which probably results from the effect of spark plasma sintering technology (pressure and current along the same direction during consolidation) but also from a significant contribution of diffusion with mass transfer along the particle boundaries in the composite.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The paper presents a study of interdiffusion processes in a binary Fe-Ni system (obtained by electroconsolidation of nickel and iron powders) by X-ray energy dispersive spectroscopy. Well-separated regions of almost pure iron and nickel have been discovered. The content of nickel, estimated from the concentration dependence of the interdiffusion coefficient, which determines the kinetics of the homogenization process of the electroconsolidated Fe-Ni composite sample, was ~70 at.%. The value of the interdiffusion coefficient of the electroconsolidated Fe-Ni composite is significantly higher than that of the alloy of similar composition which probably results from the effect of spark plasma sintering technology (pressure and current along the same direction during consolidation) but also from a significant contribution of diffusion with mass transfer along the particle boundaries in the composite. |
| 5. | Ye-Hong Chen, Wei Qin, Xin Wang, Adam Miranowicz, Franco Nori Phys. Rev. Lett., 126 , pp. 023602, 2021. @article{PhysRevLett.126.023602, title = {Shortcuts to Adiabaticity for the Quantum Rabi Model: Efficient Generation of Giant Entangled Cat States via Parametric Amplification}, author = {Ye-Hong Chen and Wei Qin and Xin Wang and Adam Miranowicz and Franco Nori}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.126.023602}, doi = {10.1103/PhysRevLett.126.023602}, year = {2021}, date = {2021-01-14}, journal = {Phys. Rev. Lett.}, volume = {126}, pages = {023602}, publisher = {American Physical Society}, abstract = {We propose a method for the fast generation of nonclassical ground states of the Rabi model in the ultrastrong and deep-strong coupling regimes via the shortcuts-to-adiabatic (STA) dynamics. The time-dependent quantum Rabi model is simulated by applying parametric amplification to the Jaynes-Cummings model. Using experimentally feasible parametric drive, this STA protocol can generate large-size Schrödinger cat states, through a process that is ∼10 times faster compared to adiabatic protocols. Such fast evolution increases the robustness of our protocol against dissipation. Our method enables one to freely design the parametric drive, so that the target state can be generated in the lab frame. A largely detuned light-matter coupling makes the protocol robust against imperfections of the operation times in experiments.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We propose a method for the fast generation of nonclassical ground states of the Rabi model in the ultrastrong and deep-strong coupling regimes via the shortcuts-to-adiabatic (STA) dynamics. The time-dependent quantum Rabi model is simulated by applying parametric amplification to the Jaynes-Cummings model. Using experimentally feasible parametric drive, this STA protocol can generate large-size Schrödinger cat states, through a process that is ∼10 times faster compared to adiabatic protocols. Such fast evolution increases the robustness of our protocol against dissipation. Our method enables one to freely design the parametric drive, so that the target state can be generated in the lab frame. A largely detuned light-matter coupling makes the protocol robust against imperfections of the operation times in experiments. |
| 4. | Joanna K. Kalaga, Anna Kowalewska-Kudłaszyk, Mateusz Nowotarski, Wiesław Leoński Violation of Leggett–Garg Inequalities in a Kerr-Type Chaotic System Photonics, 8 (1), pp. 20, 2021. @article{Kalaga2021, title = {Violation of Leggett–Garg Inequalities in a Kerr-Type Chaotic System}, author = {Joanna K. Kalaga and Anna Kowalewska-Kudłaszyk and Mateusz Nowotarski and Wiesław Leoński}, url = {https://doi.org/10.3390/photonics8010020}, doi = {10.3390/photonics8010020}, year = {2021}, date = {2021-01-12}, journal = {Photonics}, volume = {8}, number = {1}, pages = {20}, publisher = {MDPI AG}, abstract = {We consider a quantum nonlinear Kerr-like oscillator externally pumped by a series of ultrashort coherent pulses to analyze the quantum time-correlations appearing while the system evolves. For that purpose, we examine the violation of the Leggett–Garg inequality. We show how the character of such correlations changes when the system’s dynamics correspond to the regular and chaotic regions of its classical counterpart.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We consider a quantum nonlinear Kerr-like oscillator externally pumped by a series of ultrashort coherent pulses to analyze the quantum time-correlations appearing while the system evolves. For that purpose, we examine the violation of the Leggett–Garg inequality. We show how the character of such correlations changes when the system’s dynamics correspond to the regular and chaotic regions of its classical counterpart. |
| 3. | Nandan K. P. Babu, Aleksandra Trzaskowska, Piotr Graczyk, Grzegorz Centała, Szymon Mieszczak, Hubert Głowiński, Miłosz Zdunek, Sławomir Mielcarek, Jarosław W. Kłos Nano Lett., 21 (2), pp. 946-951, 2021. @article{doi:10.1021/acs.nanolett.0c03692, title = {The Interaction between Surface Acoustic Waves and Spin Waves: The Role of Anisotropy and Spatial Profiles of the Modes}, author = {Nandan K. P. Babu and Aleksandra Trzaskowska and Piotr Graczyk and Grzegorz Centała and Szymon Mieszczak and Hubert Głowiński and Miłosz Zdunek and Sławomir Mielcarek and Jarosław W. Kłos}, url = {https://doi.org/10.1021/acs.nanolett.0c03692}, doi = {10.1021/acs.nanolett.0c03692}, year = {2021}, date = {2021-01-01}, journal = {Nano Lett.}, volume = {21}, number = {2}, pages = {946-951}, abstract = {The interaction between different types of wave excitation in hybrid systems is usually anisotropic. Magnetoelastic coupling between surface acoustic waves and spin waves strongly depends on the direction of the external magnetic field. However, in the present study we observe that even if the orientation of the field is supportive for the coupling, the magnetoelastic interaction can be significantly reduced for surface acoustic waves with a particular profile in the direction normal to the surface at distances much smaller than the wavelength. We use Brillouin light scattering for the investigation of thermally excited phonons and magnons in a magnetostrictive CoFeB/Au multilayer deposited on a Si substrate. The experimental data are interpreted on the basis of a linearized model of interaction between surface acoustic waves and spin waves.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The interaction between different types of wave excitation in hybrid systems is usually anisotropic. Magnetoelastic coupling between surface acoustic waves and spin waves strongly depends on the direction of the external magnetic field. However, in the present study we observe that even if the orientation of the field is supportive for the coupling, the magnetoelastic interaction can be significantly reduced for surface acoustic waves with a particular profile in the direction normal to the surface at distances much smaller than the wavelength. We use Brillouin light scattering for the investigation of thermally excited phonons and magnons in a magnetostrictive CoFeB/Au multilayer deposited on a Si substrate. The experimental data are interpreted on the basis of a linearized model of interaction between surface acoustic waves and spin waves. |
| 2. | Ricarda Pütt, Piotr Kozłowski, Irina Werner, Jan Griebel, Sebastian Schmitz, Jonas Warneke, Kirill Yu. Monakhov P2V3W15-Polyoxometalates Functionalized with Phthalocyaninato Y and Yb Moieties Inorg. Chem. , 60 (1), pp. 80-86, 2021, (PMID: 33180468). @article{Putt, title = {P2V3W15-Polyoxometalates Functionalized with Phthalocyaninato Y and Yb Moieties}, author = {Ricarda Pütt and Piotr Kozłowski and Irina Werner and Jan Griebel and Sebastian Schmitz and Jonas Warneke and Kirill Yu. Monakhov}, url = {https://doi.org/10.1021/acs.inorgchem.0c02257}, doi = {10.1021/acs.inorgchem.0c02257}, year = {2021}, date = {2021-01-01}, journal = {Inorg. Chem. }, volume = {60}, number = {1}, pages = {80-86}, abstract = {A tris(alkoxo)pyridine-augmented Wells–Dawson polyoxometalate (nBu4N)6[WD-Py] (WD = P2V3W15O59(OCH2)3C, Py = C5H4N) was functionalized with phthalocyaninato metal moieties (MPc where M = Y or Yb and Pc = C32H16N8) to afford (nBu4N)4[HWD-Py(MPc)] compounds. High-resolution mass spectrometry was used to detect and identify the hybrid assembly. The magnetism studies reveal substantial differences between M = Yb (monomeric, single-ion paramagnetism) and M = Y (containing dimers, radical character). The results of electronic paramagnetic resonance spectroscopy, SQUID magnetometry, and magnetochemical calculations indicate the presence of intramolecular charge transfer from the MPc moiety to the polyoxometalate and of intermolecular charge transfer from the MPc moiety of one molecule to the polyoxometalate unit of another molecule. These compounds with identified VIV ions represent unique examples of transition-metal/lanthanide complex-POM hybrid compounds with nonphotoinduced charge transfer between electron donor and acceptor centers.}, note = {PMID: 33180468}, keywords = {}, pubstate = {published}, tppubtype = {article} } A tris(alkoxo)pyridine-augmented Wells–Dawson polyoxometalate (nBu4N)6[WD-Py] (WD = P2V3W15O59(OCH2)3C, Py = C5H4N) was functionalized with phthalocyaninato metal moieties (MPc where M = Y or Yb and Pc = C32H16N8) to afford (nBu4N)4[HWD-Py(MPc)] compounds. High-resolution mass spectrometry was used to detect and identify the hybrid assembly. The magnetism studies reveal substantial differences between M = Yb (monomeric, single-ion paramagnetism) and M = Y (containing dimers, radical character). The results of electronic paramagnetic resonance spectroscopy, SQUID magnetometry, and magnetochemical calculations indicate the presence of intramolecular charge transfer from the MPc moiety to the polyoxometalate and of intermolecular charge transfer from the MPc moiety of one molecule to the polyoxometalate unit of another molecule. These compounds with identified VIV ions represent unique examples of transition-metal/lanthanide complex-POM hybrid compounds with nonphotoinduced charge transfer between electron donor and acceptor centers. |
| 1. | Sławomir Mielcarek, A. Majchrowski Growth of ABO3 and BO2 crystals (in book: Switching effects in transition metals oxides) Szot, K S, Krok, F, Roleder, K (Ed.): Chapter 2, PWN, 2021. @inbook{switching_effects, title = {Growth of ABO3 and BO2 crystals (in book: Switching effects in transition metals oxides)}, author = {Sławomir Mielcarek and A. Majchrowski}, editor = {K. S. Szot and F. Krok and K. Roleder}, year = {2021}, date = {2021-01-01}, publisher = {PWN}, chapter = {2}, abstract = {Structural quality as well as stoichiometry of crystalline materials are the main factors influencing their physical properties, and therefore decide on their potential applications. Bulk crystallization of many oxide perovskites suffers from many drawbacks due to properties of melts, existing high-temperature phase transitions, and non-stoichiometry, among others. However, tremendous progress in thin-film and other structure technologies allows, mainly due to vapor techniques, fabrication of high-quality samples for further investigations and applications. Understanding of thermodynamics and kinetics of crystal growth, nucleation processes, and knowledge of proper crystal growth techniques is essential to obtain good quality crystals. The chapter is mainly devoted to crystal growth techniques of chosen oxide crystals. The theory of crystal growth, due to limited space, is described in short. Given references will allow the reader a full view into its complexity and many aspects of phenomena connected with crystallization. In the last part of the chapter methods of analysis of as-grown crystals are described.}, keywords = {}, pubstate = {published}, tppubtype = {inbook} } Structural quality as well as stoichiometry of crystalline materials are the main factors influencing their physical properties, and therefore decide on their potential applications. Bulk crystallization of many oxide perovskites suffers from many drawbacks due to properties of melts, existing high-temperature phase transitions, and non-stoichiometry, among others. However, tremendous progress in thin-film and other structure technologies allows, mainly due to vapor techniques, fabrication of high-quality samples for further investigations and applications. Understanding of thermodynamics and kinetics of crystal growth, nucleation processes, and knowledge of proper crystal growth techniques is essential to obtain good quality crystals. The chapter is mainly devoted to crystal growth techniques of chosen oxide crystals. The theory of crystal growth, due to limited space, is described in short. Given references will allow the reader a full view into its complexity and many aspects of phenomena connected with crystallization. In the last part of the chapter methods of analysis of as-grown crystals are described. |