Dr hab. Konrad J. Kapcia, prof. UAM

Dr hab. Konrad J. Kapcia, prof. UAM

Head of Department of Theory of Condensed Matter

Tel: +48 61 829 5051
Loc: wing D, first floor, room 108
Email: konrad.kapcia@amu.edu.pl
URL: https://kakonrad.wordpress.com

Scientific degrees

Habilitation in physics – 2022
PhD in physics (with distinction) – 2014
M.Sc. in theoretical physics (with distinction) – 2009

Research interests

Keywords: condensed matter physics, strongly correlated systems, ultracold atomic gases on the lattice, unconventional superconductivity, magnetic ordering in solids, ab initio calculations, density functional theory, quantum dots, Fano and Majorana physics, ultrafast phenomena, molecular dynamics, x-rays

Research stays

2021/2023 – Center for Free-Electron Laser Science (CFEL-DESY), Hamburg, Germany
2019/2020 – Center for Free-Electron Laser Science (CFEL-DESY), Hamburg, Germany
2015 – International School of Advanced Studies, Triesre, Italy

Scientific achievements

2019 – Fellowship of the Polish Ministry of Science and Higher Education for outstanding young scientists
2014 – Scholarship for young scientists granted by the city of Poznań
2013 – Scholarship of the Foundation of A. Mickiewicz University in Poznań

Projects

Konrad J. Kapcia

Modeling of ultrafast electronic processes in selected condensed matter systems and quantum dots

2024 - 2025, (National Component of the Mieczysław Bekker program (2020 edition) of the National Agency for Academic Exchange (NAWA), BPN/BKK/2022/1/00011, budget: 102 000 PLN).

Konrad J. Kapcia

Modeling of ultrafast X-ray induced demagnetization in magnetic materials

2023 - 2021, (BEKKER 3rd edition (2020), Polish National Agency for Academic Exchange, budget: 345 000 PLN).

Publications

2024
18.	Viktoriia Drushliak, Konrad J. Kapcia, Marek Szafrański White-Light Emission Triggered by Pseudo Jahn-Teller Distortion at the Pressure-Induced Phase Transition in Cs4PbBr6 Journal of Materials Chemistry C, 12 (12), pp. 4360-4368, 2024. Links \| BibTeX @article{Drushliak2024, title = {White-Light Emission Triggered by Pseudo Jahn-Teller Distortion at the Pressure-Induced Phase Transition in Cs4PbBr6}, author = {Viktoriia Drushliak and Konrad J. Kapcia and Marek Szafrański}, doi = {10.1039/D4TC00036F}, year = {2024}, date = {2024-02-20}, journal = {Journal of Materials Chemistry C}, volume = {12}, number = {12}, pages = {4360-4368}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close doi:10.1039/D4TC00036F Close
17.	Konrad J. Kapcia, Jan Barański Magnetic and charge orders on the triangular lattice: Extended Hubbard model with intersite Ising-like magnetic interactions in the atomic limit Journal of Magnetism and Magnetic Materials, 591 , pp. 171702, 2024. Links \| BibTeX @article{Kapcia2024c, title = {Magnetic and charge orders on the triangular lattice: Extended Hubbard model with intersite Ising-like magnetic interactions in the atomic limit}, author = {Konrad J. Kapcia and Jan Barański}, doi = {10.1016/j.jmmm.2023.171702}, year = {2024}, date = {2024-02-01}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {591}, pages = {171702}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close doi:10.1016/j.jmmm.2023.171702 Close
16.	Konrad J. Kapcia, V. Tkachenko, F. Capotondi, A. Lichtenstein, S. Molodtsov, P. Piekarz, B. Ziaja Ultrafast demagnetization in bulk nickel induced by X-ray photons tuned to Ni M3 and L3 absorption edges Scientific Reports, 14 , pp. 473, 2024. Links \| BibTeX @article{Kapcia2024b, title = {Ultrafast demagnetization in bulk nickel induced by X-ray photons tuned to Ni M3 and L3 absorption edges}, author = {Konrad J. Kapcia and V. Tkachenko and F. Capotondi and A. Lichtenstein and S. Molodtsov and P. Piekarz and B. Ziaja}, doi = {10.1038/s41598-023-50467-9}, year = {2024}, date = {2024-01-04}, journal = {Scientific Reports}, volume = {14}, pages = {473}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close doi:10.1038/s41598-023-50467-9 Close
15.	Agnieszka Cichy, Konrad J. Kapcia, Andrzej Ptok Spin-polarized superconducting phase in semiconducting system with next-nearest-neighbor hopping on the honeycomb lattice J. Magn. Magn. Mater., 589 , pp. 171522, 2024. Links \| BibTeX @article{Cichy2024, title = {Spin-polarized superconducting phase in semiconducting system with next-nearest-neighbor hopping on the honeycomb lattice}, author = {Agnieszka Cichy and Konrad J. Kapcia and Andrzej Ptok}, doi = {10.1016/j.jmmm.2023.171522}, year = {2024}, date = {2024-01-01}, journal = {J. Magn. Magn. Mater.}, volume = {589}, pages = {171522}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close doi:10.1016/j.jmmm.2023.171522 Close
14.	Konrad J. Kapcia, V. Lipp, V. Tkachenko, B. Ziaja Theoretical analysis of X-Ray Free-Electron-Laser Experimental Data Using Monte-Carlo and Molecular-Dynamics Based Computational Tools Comprehensive Computational Chemistry (First Edition), 3 , pp. 858-864, 2024. Links \| BibTeX @article{Kapcia2024, title = {Theoretical analysis of X-Ray Free-Electron-Laser Experimental Data Using Monte-Carlo and Molecular-Dynamics Based Computational Tools}, author = {Konrad J. Kapcia and V. Lipp and V. Tkachenko and B. Ziaja}, doi = {10.1016/B978-0-12-821978-2.00110-0}, year = {2024}, date = {2024-01-01}, journal = {Comprehensive Computational Chemistry (First Edition)}, volume = {3}, pages = {858-864}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close doi:10.1016/B978-0-12-821978-2.00110-0 Close
2023
13.	J. Barański, M. Barańska, T. Zienkiewicz, J. Tomaszewska, Konrad J. Kapcia Continuous unitary transformation approach to the Kondo-Majorana interplay J. Magn. Magn. Mater., 588 , pp. 171464, 2023. Links \| BibTeX @article{Barański2023c, title = {Continuous unitary transformation approach to the Kondo-Majorana interplay}, author = {J. Barański and M. Barańska and T. Zienkiewicz and J. Tomaszewska and Konrad J. Kapcia}, doi = {10.1016/j.jmmm.2023.171464}, year = {2023}, date = {2023-12-15}, journal = {J. Magn. Magn. Mater.}, volume = {588}, pages = {171464}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close doi:10.1016/j.jmmm.2023.171464 Close
12.	B. Ziaja, M. Stransky, Konrad J. Kapcia, I. Inoue Modeling Femtosecond Reduction of Atomic Scattering Factors in X-ray-Excited Silicon with Boltzmann Kinetic Equations Atoms, 11 (12), pp. 154, 2023. Links \| BibTeX @article{Ziaja2023, title = {Modeling Femtosecond Reduction of Atomic Scattering Factors in X-ray-Excited Silicon with Boltzmann Kinetic Equations}, author = {B. Ziaja and M. Stransky and Konrad J. Kapcia and I. Inoue}, doi = {10.3390/atoms11120154}, year = {2023}, date = {2023-12-07}, journal = {Atoms}, volume = {11}, number = {12}, pages = {154}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close doi:10.3390/atoms11120154 Close
11.	M. Biernacka, P. Butkiewicz, Konrad J. Kapcia, W. Olszewski, D. Satuła, M. Szafrański, M. Wojtyniak, K. R. Szymański Electrical polarization switch in bulk single-crystal GaFeO3 Phys. Rev. B, 108 (19), pp. 195101, 2023. Links \| BibTeX @article{Biernacka2023, title = {Electrical polarization switch in bulk single-crystal GaFeO3}, author = {M. Biernacka and P. Butkiewicz and Konrad J. Kapcia and W. Olszewski and D. Satuła and M. Szafrański and M. Wojtyniak and K. R. Szymański}, doi = {10.1103/PhysRevB.108.195101}, year = {2023}, date = {2023-11-01}, journal = {Phys. Rev. B}, volume = {108}, number = {19}, pages = {195101}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close doi:10.1103/PhysRevB.108.195101 Close
10.	P. Heimann, N. J. Hartley, I. Inoue, V. Tkachenko, A. Antoine, F. Dorchies, R. Falcone, J. Gaudin, H. Höppner, Y. Inubushi, Konrad J. Kapcia, H. J. Lee, V. Lipp, P. Martinez, N. Medvedev, F. Tavella, S. Toleikis, M. Yabashi, T. Yabuuchi, J. Yamada, B. Ziaja Non-thermal structural transformation of diamond driven by x-rays Struct. Dyn., 10 (5), pp. 054502, 2023. Links \| BibTeX @article{Heimann2023, title = {Non-thermal structural transformation of diamond driven by x-rays}, author = {P. Heimann and N. J. Hartley and I. Inoue and V. Tkachenko and A. Antoine and F. Dorchies and R. Falcone and J. Gaudin and H. Höppner and Y. Inubushi and Konrad J. Kapcia and H. J. Lee and V. Lipp and P. Martinez and N. Medvedev and F. Tavella and S. Toleikis and M. Yabashi and T. Yabuuchi and J. Yamada and B. Ziaja}, doi = {10.1063/4.0000193}, year = {2023}, date = {2023-10-27}, journal = {Struct. Dyn.}, volume = {10}, number = {5}, pages = {054502}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close doi:10.1063/4.0000193 Close
9.	Ichiro Inoue, Jumpei Yamada, Konrad J. Kapcia, Michal Stransky, Victor Tkachenko, Zoltan Jurek, Takato Inoue, Taito Osaka, Yuichi Inubushi, Atsuki Ito, Yuto Tanaka, Satoshi Matsuyama, Kazuto Yamauchi, Makina Yabashi, Beata Ziaja Femtosecond Reduction of Atomic Scattering Factors Triggered by Intense X-Ray Pulse Physical Review Letters, 131 , pp. 163201, 2023. Abstract \| Links \| BibTeX @article{Inoue2023, title = {Femtosecond Reduction of Atomic Scattering Factors Triggered by Intense X-Ray Pulse}, author = {Ichiro Inoue and Jumpei Yamada and Konrad J. Kapcia and Michal Stransky and Victor Tkachenko and Zoltan Jurek and Takato Inoue and Taito Osaka and Yuichi Inubushi and Atsuki Ito and Yuto Tanaka and Satoshi Matsuyama and Kazuto Yamauchi and Makina Yabashi and Beata Ziaja}, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.163201}, doi = {10.1103/PhysRevLett.131.163201}, year = {2023}, date = {2023-10-17}, journal = {Physical Review Letters}, volume = {131}, pages = {163201}, abstract = {X-ray diffraction of silicon irradiated with tightly focused femtosecond x-ray pulses (photon energy, 11.5 keV; pulse duration, 6 fs) was measured at various x-ray intensities up to 4.6×10^19W/cm^2. The measurement reveals that the diffraction intensity is highly suppressed when the x-ray intensity reaches of the order of 10^19W/cm^2. With a dedicated simulation, we confirm that the observed reduction of the diffraction intensity can be attributed to the femtosecond change in individual atomic scattering factors due to the ultrafast creation of highly ionized atoms through photoionization, Auger decay, and subsequent collisional ionization. We anticipate that this ultrafast reduction of atomic scattering factor will be a basis for new x-ray nonlinear techniques, such as pulse shortening and contrast variation x-ray scattering.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close X-ray diffraction of silicon irradiated with tightly focused femtosecond x-ray pulses (photon energy, 11.5 keV; pulse duration, 6 fs) was measured at various x-ray intensities up to 4.6×10^19W/cm^2. The measurement reveals that the diffraction intensity is highly suppressed when the x-ray intensity reaches of the order of 10^19W/cm^2. With a dedicated simulation, we confirm that the observed reduction of the diffraction intensity can be attributed to the femtosecond change in individual atomic scattering factors due to the ultrafast creation of highly ionized atoms through photoionization, Auger decay, and subsequent collisional ionization. We anticipate that this ultrafast reduction of atomic scattering factor will be a basis for new x-ray nonlinear techniques, such as pulse shortening and contrast variation x-ray scattering. Close https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.163201 doi:10.1103/PhysRevLett.131.163201 Close
8.	Flavio Capotondi, Alexander Lichtenstein, Serguei Molodtsov, Leonard Mueller, Andre Philippi-Kobs, Przemysław Piekarz, Konrad J. Kapcia, Victor Tkachenko, Beata Ziaja Electronic processes occurring during ultrafast demagnetization of cobalt triggered by x-ray photons tuned to the Co $L_3$ resonance Phys. Rev. B, 107 , pp. 094402, 2023. Links \| BibTeX @article{PhysRevB.107.094402, title = {Electronic processes occurring during ultrafast demagnetization of cobalt triggered by x-ray photons tuned to the Co $L_3$ resonance}, author = {Flavio Capotondi and Alexander Lichtenstein and Serguei Molodtsov and Leonard Mueller and Andre Philippi-Kobs and Przemysław Piekarz and Konrad J. Kapcia and Victor Tkachenko and Beata Ziaja}, url = {https://link.aps.org/doi/10.1103/PhysRevB.107.094402}, doi = {10.1103/PhysRevB.107.094402}, year = {2023}, date = {2023-03-01}, journal = {Phys. Rev. B}, volume = {107}, pages = {094402}, publisher = {American Physical Society}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close https://link.aps.org/doi/10.1103/PhysRevB.107.094402 doi:10.1103/PhysRevB.107.094402 Close
7.	Jan Barański, Magaldena Barańska, Tomasz Zienkiewicz, Konrad J. Kapcia Quench dynamics of Fano-like resonances in the presence of the on-dot superconducting pairing Scientific Reports, 13 (1), pp. 7639, 2023, ISSN: 2045-2322. Abstract \| Links \| BibTeX @article{Baranski2023, title = {Quench dynamics of Fano-like resonances in the presence of the on-dot superconducting pairing}, author = {Jan Bara{ń}ski and Magaldena Bara{ń}ska and Tomasz Zienkiewicz and Konrad J. Kapcia}, url = {https://doi.org/10.1038/s41598-023-34376-5}, doi = {10.1038/s41598-023-34376-5}, issn = {2045-2322}, year = {2023}, date = {2023-01-01}, journal = {Scientific Reports}, volume = {13}, number = {1}, pages = {7639}, abstract = {We explore the electron dynamics of a system composed of double quantum dot embedded between metallic and superconducting leads in a “T-shape” geometry. In nanoscopic systems, where electron transfer between electrodes can be realized via different paths, interference effects play an important role. For double quantum dot system in the chosen geometry, interference of electrons transferred between electrodes via the interfacial quantum dot and electrons scattered on the side dot gives rise to Fano-like interference. If such a system is additionally coupled to a superconducting electrode, together with the well-understood Fano resonance an additional resonance appears on the opposite side of the Fermi level. In the recent work (Barański et al. in Sci Rep 10:2881, 2020), we showed that this resonance occurs solely as a result of the local pairing of non-scattered electrons with scattered ones. In this work, considering the quench dynamics, we explore how much time is required for formation of each of these resonances. In particular, (i) we analyze the charge oscillations between subsystems; (ii) we estimate the time required for each resonance to achieve stable equilibrium upon an abrupt change of interdot connection; (iii) we discuss a typical energy and time scales for experiments on similar architectures.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close We explore the electron dynamics of a system composed of double quantum dot embedded between metallic and superconducting leads in a “T-shape” geometry. In nanoscopic systems, where electron transfer between electrodes can be realized via different paths, interference effects play an important role. For double quantum dot system in the chosen geometry, interference of electrons transferred between electrodes via the interfacial quantum dot and electrons scattered on the side dot gives rise to Fano-like interference. If such a system is additionally coupled to a superconducting electrode, together with the well-understood Fano resonance an additional resonance appears on the opposite side of the Fermi level. In the recent work (Barański et al. in Sci Rep 10:2881, 2020), we showed that this resonance occurs solely as a result of the local pairing of non-scattered electrons with scattered ones. In this work, considering the quench dynamics, we explore how much time is required for formation of each of these resonances. In particular, (i) we analyze the charge oscillations between subsystems; (ii) we estimate the time required for each resonance to achieve stable equilibrium upon an abrupt change of interdot connection; (iii) we discuss a typical energy and time scales for experiments on similar architectures. Close https://doi.org/10.1038/s41598-023-34376-5 doi:10.1038/s41598-023-34376-5 Close
6.	Jakub Skórka, Konrad J. Kapcia, Paweł T. Jochym, Andrzej Ptok Chiral phonons in binary compounds ABi (A = K, Rb, Cs) with P21/c structure Materials Today Communications, 35 , pp. 105888, 2023, ISSN: 2352-4928. Abstract \| Links \| BibTeX @article{SKORKA2023105888, title = {Chiral phonons in binary compounds ABi (A = K, Rb, Cs) with P21/c structure}, author = {Jakub Skórka and Konrad J. Kapcia and Paweł T. Jochym and Andrzej Ptok}, url = {https://www.sciencedirect.com/science/article/pii/S2352492823005792}, doi = {https://doi.org/10.1016/j.mtcomm.2023.105888}, issn = {2352-4928}, year = {2023}, date = {2023-01-01}, journal = {Materials Today Communications}, volume = {35}, pages = {105888}, abstract = {Binary compounds ABi (A = K, Rb, Cs) crystallize in P21/c structure containing both clockwise and anticlockwise chiral chains of Bi atoms. Electronic band structure exhibits the insulating nature of these systems, with the band gap about 0.25eV. The presented study of dynamical properties confirm a stability of the system with P21/c symmetry. The crystal structure contains the quasi-one-dimensional Bi chains, exhibiting four-fold-like rotational “local” symmetry. Nevertheless, the system formally possesses two-fold rotational symmetry. Independently of the absence of the three-fold (or higher) rotational symmetry axes for the whole crystal, the chiral modes propagate along the Bi atom chains in these systems. We discuss basic properties of these modes in monoatomic chiral chains. We show that the two-fold rotational symmetry axis affects the main properties of the chiral phonons, which are not realized at the high-symmetry points, but along some paths between them in the reciprocal space. In addition, in the doped system, the chiral phonons possess non-zero total angular momentum.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Binary compounds ABi (A = K, Rb, Cs) crystallize in P21/c structure containing both clockwise and anticlockwise chiral chains of Bi atoms. Electronic band structure exhibits the insulating nature of these systems, with the band gap about 0.25eV. The presented study of dynamical properties confirm a stability of the system with P21/c symmetry. The crystal structure contains the quasi-one-dimensional Bi chains, exhibiting four-fold-like rotational “local” symmetry. Nevertheless, the system formally possesses two-fold rotational symmetry. Independently of the absence of the three-fold (or higher) rotational symmetry axes for the whole crystal, the chiral modes propagate along the Bi atom chains in these systems. We discuss basic properties of these modes in monoatomic chiral chains. We show that the two-fold rotational symmetry axis affects the main properties of the chiral phonons, which are not realized at the high-symmetry points, but along some paths between them in the reciprocal space. In addition, in the doped system, the chiral phonons possess non-zero total angular momentum. Close https://www.sciencedirect.com/science/article/pii/S2352492823005792 doi:https://doi.org/10.1016/j.mtcomm.2023.105888 Close
5.	Jan Barański, Konrad J. Kapcia Dynamics of Fano-Like Resonances in Double-Quantum-Dot Systems Acta Physica Polonica A, 143 (2), pp. 143, 2023. Abstract \| Links \| BibTeX @article{Jan_Baranski2023-id, title = {Dynamics of Fano-Like Resonances in Double-Quantum-Dot Systems}, author = {Jan Barański and Konrad J. Kapcia}, url = {http://appol.ifpan.edu.pl/index.php/appa/article/view/143_143}, year = {2023}, date = {2023-01-01}, journal = {Acta Physica Polonica A}, volume = {143}, number = {2}, pages = {143}, abstract = {Quantum interference effects appearing in mesoscopic heterostructures have been extensively studied in static conditions over the last decades. It is interesting to examine the dynamics of these phenomena and get insight into the process of the formation of interference patterns. In this work, we analyze the time required for the formation of Fano-like resonances in a double quantum dot system. We examined the time evolution of conductance upon establishing an abrupt connection between quantum dots. Asymmetric Fano lines are characterized by the close coexistence of resonant enhancement and resonant suppression. Therefore, we pay particular attention to voltages, which in the static case, correspond to both these features. Our research shows that the analyzed resonances are characterized by two time scales: (i) the first one related to charge oscillations between subsystems and mostly governed by the interdot coupling constant and the relative position of energy levels of quantum dots, and (ii) the second one associated to the electron scattering on a continuum of states and responsible for the relaxation. We also show that the time required for achieving a static solution is different for voltages corresponding to local minima and local maxima.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Quantum interference effects appearing in mesoscopic heterostructures have been extensively studied in static conditions over the last decades. It is interesting to examine the dynamics of these phenomena and get insight into the process of the formation of interference patterns. In this work, we analyze the time required for the formation of Fano-like resonances in a double quantum dot system. We examined the time evolution of conductance upon establishing an abrupt connection between quantum dots. Asymmetric Fano lines are characterized by the close coexistence of resonant enhancement and resonant suppression. Therefore, we pay particular attention to voltages, which in the static case, correspond to both these features. Our research shows that the analyzed resonances are characterized by two time scales: (i) the first one related to charge oscillations between subsystems and mostly governed by the interdot coupling constant and the relative position of energy levels of quantum dots, and (ii) the second one associated to the electron scattering on a continuum of states and responsible for the relaxation. We also show that the time required for achieving a static solution is different for voltages corresponding to local minima and local maxima. Close http://appol.ifpan.edu.pl/index.php/appa/article/view/143_143 Close
2022
4.	Konrad J. Kapcia, V. Tkachenko, F. Capotondi, A. Lichtenstein, S. Molodtsov, L. Müller, A. Philippi-Kobs, P. Piekarz, B. Ziaja Modeling of ultrafast X-ray induced magnetization dynamics in magnetic multilayer systems npj Computational Materials, 8 , pp. 212, 2022. Abstract \| Links \| BibTeX @article{Kapcia2022, title = {Modeling of ultrafast X-ray induced magnetization dynamics in magnetic multilayer systems}, author = {Konrad J. Kapcia and V. Tkachenko and F. Capotondi and A. Lichtenstein and S. Molodtsov and L. Müller and A. Philippi-Kobs and P. Piekarz and B. Ziaja}, url = {https://www.nature.com/articles/s41524-022-00895-4}, doi = {10.1038/s41524-022-00895-4}, year = {2022}, date = {2022-10-01}, journal = {npj Computational Materials}, volume = {8}, pages = {212}, abstract = {In this work, we report on modeling results obtained with our recently developed simulation tool enabling nanoscopic description of electronic processes in X-ray irradiated ferromagnetic materials. With this tool, we have studied the response of Co/Pt multilayer system irradiated by an ultrafast extreme ultraviolet pulse at the M-edge of Co (photon energy ~60 eV). It was previously investigated experimentally at the FERMI free-electron-laser facility, using the magnetic small-angle X-ray scattering technique. Our simulations show that the magnetic scattering signal from cobalt decreases on femtosecond timescales due to electronic excitation, relaxation, and transport processes both in the cobalt and in the platinum layers, following the trend observed in the experimental data. The confirmation of the predominant role of electronic processes for X-ray induced demagnetization in the regime below the structural damage threshold is a step toward quantitative control and manipulation of X-ray induced magnetic processes on femtosecond timescales.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close In this work, we report on modeling results obtained with our recently developed simulation tool enabling nanoscopic description of electronic processes in X-ray irradiated ferromagnetic materials. With this tool, we have studied the response of Co/Pt multilayer system irradiated by an ultrafast extreme ultraviolet pulse at the M-edge of Co (photon energy ~60 eV). It was previously investigated experimentally at the FERMI free-electron-laser facility, using the magnetic small-angle X-ray scattering technique. Our simulations show that the magnetic scattering signal from cobalt decreases on femtosecond timescales due to electronic excitation, relaxation, and transport processes both in the cobalt and in the platinum layers, following the trend observed in the experimental data. The confirmation of the predominant role of electronic processes for X-ray induced demagnetization in the regime below the structural damage threshold is a step toward quantitative control and manipulation of X-ray induced magnetic processes on femtosecond timescales. Close https://www.nature.com/articles/s41524-022-00895-4 doi:10.1038/s41524-022-00895-4 Close
3.	Miłosz Rybak, Tomasz Woźniak, Magdalena Birowska, Filip Dybała, Alfredo Segura, Konrad J. Kapcia, Paweł Scharoch, Robert Kudrawiec Stress-Tuned Optical Transitions in Layered 1T-MX2 (M=Hf, Zr, Sn; X=S, Se) Crystals Nanomaterials, 12 (19), pp. 3433, 2022. Abstract \| Links \| BibTeX @article{Rybak2022, title = {Stress-Tuned Optical Transitions in Layered 1T-MX2 (M=Hf, Zr, Sn; X=S, Se) Crystals }, author = {Miłosz Rybak and Tomasz Woźniak and Magdalena Birowska and Filip Dybała and Alfredo Segura and Konrad J. Kapcia and Paweł Scharoch and Robert Kudrawiec}, url = {https://www.mdpi.com/2079-4991/12/19/3433}, doi = {10.3390/nano12193433}, year = {2022}, date = {2022-09-30}, journal = {Nanomaterials}, volume = {12}, number = {19}, pages = {3433}, abstract = {Optical measurements under externally applied stresses allow us to study the materials’ electronic structure by comparing the pressure evolution of optical peaks obtained from experiments and theoretical calculations. We examine the stress-induced changes in electronic structure for the thermodynamically stable 1T polytype of selected MX2 compounds (M=Hf, Zr, Sn; X=S, Se), using the density functional theory. We demonstrate that considered 1T-MX2 materials are semiconducting with indirect character of the band gap, irrespective to the employed pressure as predicted using modified Becke–Johnson potential. We determine energies of direct interband transitions between bands extrema and in band-nesting regions close to Fermi level. Generally, the studied transitions are optically active, exhibiting in-plane polarization of light. Finally, we quantify their energy trends under external hydrostatic, uniaxial, and biaxial stresses by determining the linear pressure coefficients. Generally, negative pressure coefficients are obtained implying the narrowing of the band gap. The semiconducting-to-metal transition are predicted under hydrostatic pressure. We discuss these trends in terms of orbital composition of involved electronic bands. In addition, we demonstrate that the measured pressure coefficients of HfS2 and HfSe2 absorption edges are in perfect agreement with our predictions. Comprehensive and easy-to-interpret tables containing the optical features are provided to form the basis for assignation of optical peaks in future measurements.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Optical measurements under externally applied stresses allow us to study the materials’ electronic structure by comparing the pressure evolution of optical peaks obtained from experiments and theoretical calculations. We examine the stress-induced changes in electronic structure for the thermodynamically stable 1T polytype of selected MX2 compounds (M=Hf, Zr, Sn; X=S, Se), using the density functional theory. We demonstrate that considered 1T-MX2 materials are semiconducting with indirect character of the band gap, irrespective to the employed pressure as predicted using modified Becke–Johnson potential. We determine energies of direct interband transitions between bands extrema and in band-nesting regions close to Fermi level. Generally, the studied transitions are optically active, exhibiting in-plane polarization of light. Finally, we quantify their energy trends under external hydrostatic, uniaxial, and biaxial stresses by determining the linear pressure coefficients. Generally, negative pressure coefficients are obtained implying the narrowing of the band gap. The semiconducting-to-metal transition are predicted under hydrostatic pressure. We discuss these trends in terms of orbital composition of involved electronic bands. In addition, we demonstrate that the measured pressure coefficients of HfS2 and HfSe2 absorption edges are in perfect agreement with our predictions. Comprehensive and easy-to-interpret tables containing the optical features are provided to form the basis for assignation of optical peaks in future measurements. Close https://www.mdpi.com/2079-4991/12/19/3433 doi:10.3390/nano12193433 Close
2.	Agnieszka Cichy, Konrad J. Kapcia, Andrzej Ptok Connection between the semiconductor-superconductor transition and the spin-polarized superconducting phase in the honeycomb lattice Phys. Rev. B, 105 , pp. 214510, 2022. Abstract \| Links \| BibTeX @article{Cichy2022, title = {Connection between the semiconductor-superconductor transition and the spin-polarized superconducting phase in the honeycomb lattice}, author = {Agnieszka Cichy and Konrad J. Kapcia and Andrzej Ptok}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.105.214510}, doi = {10.1103/PhysRevB.105.214510}, year = {2022}, date = {2022-06-14}, journal = {Phys. Rev. B}, volume = {105}, pages = {214510}, abstract = {The band structure of noninteracting fermions in the honeycomb lattice exhibits the Dirac cones at the corners of the Brillouin zone. As a consequence, fermions in this lattice manifest a semiconducting behavior below some critical value of the on-site attraction Uc. However, above Uc, the superconducting phase can occur. We discuss an interplay between the semiconductor-superconductor transition and the possibility of realization of the spin-polarized superconductivity (the so-called Sarma phase). We show that the critical interaction can be tuned by the next-nearest-neighbor (NNN) hopping in the absence of the magnetic field. Moreover, a critical value of the NNN hopping exists, defining a range of parameters for which the semiconducting phase can emerge. In the weak-coupling limit case, this quantum phase transition occurs for the absolute value of the NNN hopping equal to one third of the hopping between the nearest neighbors. Similarly, in the presence of the magnetic field, the Sarma phase can appear but only in a range of parameters for which initially the semiconducting state is observed. Both of these aspects are attributed to the Lifshitz transition, which is induced by the NNN hopping as well as the external magnetic field.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close The band structure of noninteracting fermions in the honeycomb lattice exhibits the Dirac cones at the corners of the Brillouin zone. As a consequence, fermions in this lattice manifest a semiconducting behavior below some critical value of the on-site attraction Uc. However, above Uc, the superconducting phase can occur. We discuss an interplay between the semiconductor-superconductor transition and the possibility of realization of the spin-polarized superconductivity (the so-called Sarma phase). We show that the critical interaction can be tuned by the next-nearest-neighbor (NNN) hopping in the absence of the magnetic field. Moreover, a critical value of the NNN hopping exists, defining a range of parameters for which the semiconducting phase can emerge. In the weak-coupling limit case, this quantum phase transition occurs for the absolute value of the NNN hopping equal to one third of the hopping between the nearest neighbors. Similarly, in the presence of the magnetic field, the Sarma phase can appear but only in a range of parameters for which initially the semiconducting state is observed. Both of these aspects are attributed to the Lifshitz transition, which is induced by the NNN hopping as well as the external magnetic field. Close https://journals.aps.org/prb/abstract/10.1103/PhysRevB.105.214510 doi:10.1103/PhysRevB.105.214510 Close
1.	Ichiro Inoue, Victor Tkachenko, Konrad J. Kapcia, Vladimir Lipp, Beata Ziaja, Yuichi Inubushi, Toru Hara, Makina Yabashi, Eiji Nishibori Delayed Onset and Directionality of X-Ray-Induced Atomic Displacements Observed on Subatomic Length Scales Phys. Rev. Lett., 128 , pp. 223203, 2022. Abstract \| Links \| BibTeX @article{Inoue2022, title = {Delayed Onset and Directionality of X-Ray-Induced Atomic Displacements Observed on Subatomic Length Scales}, author = {Ichiro Inoue and Victor Tkachenko and Konrad J. Kapcia and Vladimir Lipp and Beata Ziaja and Yuichi Inubushi and Toru Hara and Makina Yabashi and Eiji Nishibori}, url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.223203}, doi = {10.1103/PhysRevLett.128.223203}, year = {2022}, date = {2022-06-01}, journal = {Phys. Rev. Lett.}, volume = {128}, pages = {223203}, abstract = {Transient structural changes of Al2O3 on subatomic length scales following irradiation with an intense x-ray laser pulse (photon energy: 8.70 keV; pulse duration: 6 fs; fluence: 8×102 J/cm2) have been investigated by using an x-ray pump x-ray probe technique. The measurement reveals that aluminum and oxygen atoms remain in their original positions by ∼20 fs after the intensity maximum of the pump pulse, followed by directional atomic displacements at the fixed unit cell parameters. By comparing the experimental results and theoretical simulations, we interpret that electron excitation and relaxation triggered by the pump pulse modify the potential energy surface and drives the directional atomic displacements. Our results indicate that high-resolution x-ray structural analysis with the accuracy of 0.01 Å is feasible even with intense x-ray pulses by making the pulse duration shorter than the timescale needed to complete electron excitation and relaxation processes, which usually take up to a few tens of femtoseconds.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Close Transient structural changes of Al2O3 on subatomic length scales following irradiation with an intense x-ray laser pulse (photon energy: 8.70 keV; pulse duration: 6 fs; fluence: 8×102 J/cm2) have been investigated by using an x-ray pump x-ray probe technique. The measurement reveals that aluminum and oxygen atoms remain in their original positions by ∼20 fs after the intensity maximum of the pump pulse, followed by directional atomic displacements at the fixed unit cell parameters. By comparing the experimental results and theoretical simulations, we interpret that electron excitation and relaxation triggered by the pump pulse modify the potential energy surface and drives the directional atomic displacements. Our results indicate that high-resolution x-ray structural analysis with the accuracy of 0.01 Å is feasible even with intense x-ray pulses by making the pulse duration shorter than the timescale needed to complete electron excitation and relaxation processes, which usually take up to a few tens of femtoseconds. Close https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.223203 doi:10.1103/PhysRevLett.128.223203 Close