Victor Tkachenko
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Research Subjects
Victor Tkachenko has a total of 71 co-authors. Here are the top co-authors by number of shared publications:
- Beata Ziaja
Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
14 shared publications - Konrad Jerzy Kapcia
Institute of Spintronics and Quantum Information Faculty of Physics and Astronomy Adam Mickiewicz University in Poznań Uniwersytetu Poznańskiego 2 PL-61614 Poznań Poland
8 shared publications - Vladimir Lipp
Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31-342 Kraków, Poland
6 shared publications Alexander Lichtenstein
European XFEL GmbH, Schenefeld, Germany
4 shared publicationsFlavio Capotondi
Elettra-Sincrotrone Trieste S.C.p.A, Trieste, Italy
4 shared publications- Nikita Medvedev
Institute of Physics, Czech Academy of Sciences, Prague 8, Czech Republic
4 shared publications
Latest Publications
- 7 January 2025
- Published by American Physical Society (APS) in Physical Review B
- Vol. 111 (2)
Exploring x-ray irradiation conditions for triggering ultrafast diamond graphitization
- 7 January 2025
- Published by American Physical Society (APS) in Physical Review B
- Vol. 111 (2)
Exploring x-ray irradiation conditions for triggering ultrafast diamond graphitization
- 27 September 2024
- Published by American Physical Society (APS) in Physical Review B
- Vol. 110 (10)
Interplay of thermal and nonthermal effects in x-ray-induced ultrafast melting
- 27 September 2024
- Published by American Physical Society (APS) in Physical Review B
- Vol. 110 (10)
Interplay of thermal and nonthermal effects in x-ray-induced ultrafast melting
- Open Access
- 4 January 2024
- Published by Springer Nature in Scientific Reports
- Vol. 14 (1) , 1-8
Ultrafast demagnetization in bulk nickel induced by X-ray photons tuned to Ni M3 and L3 absorption edges
Studies of light-induced demagnetization started with the experiment performed by Beaupaire et al. on Ni. Here, we present theoretical predictions for X-ray induced demagnetization of nickel, with X-ray photon energies tuned to its $$M_3$$ and $$L_3$$ absorption edges. We show that the specific feature in the density of states in the d-band of Ni, i.e., a sharp peak located just above the Fermi level, strongly influences the change of the predicted magnetic signal, making it stronger than in the previously studied case of X-ray demagnetized cobalt. It impacts also the value of Curie temperature for Ni. We believe that this finding will inspire dedicated experiments investigating magnetic processes in X-ray irradiated nickel and cobalt.- 4 January 2024
- Published by Springer Nature in Scientific Reports
- Vol. 14 (1) , 1-8
Open AccessUltrafast demagnetization in bulk nickel induced by X-ray photons tuned to Ni M3 and L3 absorption edges
Studies of light-induced demagnetization started with the experiment performed by Beaupaire et al. on Ni. Here, we present theoretical predictions for X-ray induced demagnetization of nickel, with X-ray photon energies tuned to its $$M_3$$ and $$L_3$$ absorption edges. We show that the specific feature in the density of states in the d-band of Ni, i.e., a sharp peak located just above the Fermi level, strongly influences the change of the predicted magnetic signal, making it stronger than in the previously studied case of X-ray demagnetized cobalt. It impacts also the value of Curie temperature for Ni. We believe that this finding will inspire dedicated experiments investigating magnetic processes in X-ray irradiated nickel and cobalt. - Open Access
- 1 September 2023
- Published by AIP Publishing in Structural Dynamics
- Vol. 10 (5) , 054502
Non-thermal structural transformation of diamond driven by x-rays
Intense x-ray pulses can cause the non-thermal structural transformation of diamond. At the SACLA XFEL facility, pump x-ray pulses triggered this phase transition, and probe x-ray pulses produced diffraction patterns. Time delays were observed from 0 to 250 fs, and the x-ray dose varied from 0.9 to 8.0 eV/atom. The intensity of the (111), (220), and (311) diffraction peaks decreased with time, indicating a disordering of the crystal lattice. From a Debye–Waller analysis, the rms atomic displacements perpendicular to the (111) planes were observed to be significantly larger than those perpendicular to the (220) or (311) planes. At a long time delay of 33 ms, graphite (002) diffraction indicates that graphitization did occur above a threshold dose of 1.2 eV/atom. These experimental results are in qualitative agreement with XTANT+ simulations using a hybrid model based on density-functional tight-binding molecular dynamics.
- 1 September 2023
- Published by AIP Publishing in Structural Dynamics
- Vol. 10 (5) , 054502
Open AccessNon-thermal structural transformation of diamond driven by x-rays
Intense x-ray pulses can cause the non-thermal structural transformation of diamond. At the SACLA XFEL facility, pump x-ray pulses triggered this phase transition, and probe x-ray pulses produced diffraction patterns. Time delays were observed from 0 to 250 fs, and the x-ray dose varied from 0.9 to 8.0 eV/atom. The intensity of the (111), (220), and (311) diffraction peaks decreased with time, indicating a disordering of the crystal lattice. From a Debye–Waller analysis, the rms atomic displacements perpendicular to the (111) planes were observed to be significantly larger than those perpendicular to the (220) or (311) planes. At a long time delay of 33 ms, graphite (002) diffraction indicates that graphitization did occur above a threshold dose of 1.2 eV/atom. These experimental results are in qualitative agreement with XTANT+ simulations using a hybrid model based on density-functional tight-binding molecular dynamics.
- Open Access
Interplay of thermal and non-thermal effects in x-ray-induced ultrafast melting
X-ray laser-induced structural changes in silicon undergoing femtosecond melting have been investigated by using an x-ray pump-x-ray probe technique. The experimental results for different initial sample temperatures reveal that the onset time and the speed of the atomic disordering are independent of the initial temperature, suggesting that equilibrium atomic motion in the initial state does not play a pivotal role in the x-ray-induced ultrafast melting. By comparing the observed time-dependence of the atomic disordering and the dedicated theoretical simulations, we interpret that the energy transfer from the excited electrons to ions via electron-ion coupling (thermal effect) as well as a strong modification of the interatomic potential due to electron excitations (non-thermal effect) trigger the ultrafast atomic disordering. Our finding of the interplay of thermal and non-thermal effects in the x-ray-induced melting demonstrates that accurate modeling of intense x-ray interactions with matter is essential to ensure a correct interpretation of experiments using intense x-ray laser pulses.
Open AccessInterplay of thermal and non-thermal effects in x-ray-induced ultrafast melting
X-ray laser-induced structural changes in silicon undergoing femtosecond melting have been investigated by using an x-ray pump-x-ray probe technique. The experimental results for different initial sample temperatures reveal that the onset time and the speed of the atomic disordering are independent of the initial temperature, suggesting that equilibrium atomic motion in the initial state does not play a pivotal role in the x-ray-induced ultrafast melting. By comparing the observed time-dependence of the atomic disordering and the dedicated theoretical simulations, we interpret that the energy transfer from the excited electrons to ions via electron-ion coupling (thermal effect) as well as a strong modification of the interatomic potential due to electron excitations (non-thermal effect) trigger the ultrafast atomic disordering. Our finding of the interplay of thermal and non-thermal effects in the x-ray-induced melting demonstrates that accurate modeling of intense x-ray interactions with matter is essential to ensure a correct interpretation of experiments using intense x-ray laser pulses.
- Open AccessUltrafast demagnetization in bulk nickel induced by X-ray photons tuned to Ni $M_{3}$ and $L_3$ absorption edgesStudies of light-induced demagnetization started with the experiment performed by Beaupaire et al. on nickel. Here, we present theoretical predictions for X-ray induced demagnetization of nickel, with X-ray photon energies tuned to its $M_3$ and $L_3$ absorption edges. We show that the specific feature in the density of states of the d-band of Ni, a sharp peak located just above the Fermi level, strongly influences the change of the predicted magnetic signal, making it stronger than in the previously studied case of cobalt. We believe that this finding will inspire future experiments on magnetic processes in X-ray irradiated nickel.Open AccessUltrafast demagnetization in bulk nickel induced by X-ray photons tuned to Ni $M_{3}$ and $L_3$ absorption edgesStudies of light-induced demagnetization started with the experiment performed by Beaupaire et al. on nickel. Here, we present theoretical predictions for X-ray induced demagnetization of nickel, with X-ray photon energies tuned to its $M_3$ and $L_3$ absorption edges. We show that the specific feature in the density of states of the d-band of Ni, a sharp peak located just above the Fermi level, strongly influences the change of the predicted magnetic signal, making it stronger than in the previously studied case of cobalt. We believe that this finding will inspire future experiments on magnetic processes in X-ray irradiated nickel.
- Open Access
Electronic processes occurring during ultrafast demagnetization of cobalt triggered by X-ray photons tuned to Co L$_3$ resonance
Magnetization dynamics triggered with ultrashort laser pulses has been attracting significant attention, with strong focus on the dynamics excited by VIS/NIR pulses. Only recently, strong magnetic response in solid materials induced by intense X-ray pulses from free-electron lasers (FELs) has been observed. The exact mechanisms that trigger the X-ray induced demagnetization are not yet fully understood. They are subject of on-going experimental and theoretical investigations. Here, we present a theoretical analysis of electronic processes occurring during demagnetization of Co multilayer system irradiated by X-ray pulses tuned to L$_3$-absorption edge of cobalt. We show that, similarly as in the case of X-ray induced demagnetization at M-edge of Co, electronic processes play a predominant role in the demagnetization until the pulse fluence does not exceed the structural damage threshold. The impact of electronic processes can reasonably well explain the available experimental data, without a need to introduce the mechanism of stimulated elastic forward scattering.
Open AccessElectronic processes occurring during ultrafast demagnetization of cobalt triggered by X-ray photons tuned to Co L$_3$ resonance
Magnetization dynamics triggered with ultrashort laser pulses has been attracting significant attention, with strong focus on the dynamics excited by VIS/NIR pulses. Only recently, strong magnetic response in solid materials induced by intense X-ray pulses from free-electron lasers (FELs) has been observed. The exact mechanisms that trigger the X-ray induced demagnetization are not yet fully understood. They are subject of on-going experimental and theoretical investigations. Here, we present a theoretical analysis of electronic processes occurring during demagnetization of Co multilayer system irradiated by X-ray pulses tuned to L$_3$-absorption edge of cobalt. We show that, similarly as in the case of X-ray induced demagnetization at M-edge of Co, electronic processes play a predominant role in the demagnetization until the pulse fluence does not exceed the structural damage threshold. The impact of electronic processes can reasonably well explain the available experimental data, without a need to introduce the mechanism of stimulated elastic forward scattering.
- 3 March 2023
- Published by American Physical Society (APS) in Physical Review B
- Vol. 107 (9) , 094402
Electronic processes occurring during ultrafast demagnetization of cobalt triggered by x-ray photons tuned to the Co resonanceMagnetization dynamics triggered by ultrashort laser pulses has been attracting significant attention, with a strong focus on the dynamics excited by visible/near-infrared pulses. Only recently has a strong magnetic response in solid materials induced by intense x-ray pulses from free-electron lasers been observed. The exact mechanisms that trigger the x-ray-induced demagnetization are not yet fully understood. They are the subject of ongoing experimental and theoretical investigations. Here, we present a theoretical analysis of electronic processes occurring during demagnetization of a Co multilayer system irradiated by x-ray pulses tuned to the absorption edge of cobalt. We show that, like in the case of x-ray-induced demagnetization at the edge of Co, electronic processes play a predominant role in the demagnetization until the pulse fluence does not exceed the structural damage threshold. The impact of electronic processes can explain reasonably well the available experimental data, without a need to introduce the mechanism of stimulated elastic forward scattering.- 3 March 2023
- Published by American Physical Society (APS) in Physical Review B
- Vol. 107 (9) , 094402
Electronic processes occurring during ultrafast demagnetization of cobalt triggered by x-ray photons tuned to the Co resonanceMagnetization dynamics triggered by ultrashort laser pulses has been attracting significant attention, with a strong focus on the dynamics excited by visible/near-infrared pulses. Only recently has a strong magnetic response in solid materials induced by intense x-ray pulses from free-electron lasers been observed. The exact mechanisms that trigger the x-ray-induced demagnetization are not yet fully understood. They are the subject of ongoing experimental and theoretical investigations. Here, we present a theoretical analysis of electronic processes occurring during demagnetization of a Co multilayer system irradiated by x-ray pulses tuned to the absorption edge of cobalt. We show that, like in the case of x-ray-induced demagnetization at the edge of Co, electronic processes play a predominant role in the demagnetization until the pulse fluence does not exceed the structural damage threshold. The impact of electronic processes can explain reasonably well the available experimental data, without a need to introduce the mechanism of stimulated elastic forward scattering.- Open Access
- 1 October 2022
- Published by Springer Nature in npj Computational Materials
- Vol. 8 (1) , 1-9
Modeling of ultrafast X-ray induced magnetization dynamics in magnetic multilayer systems
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.
- 1 October 2022
- Published by Springer Nature in npj Computational Materials
- Vol. 8 (1) , 1-9
Open AccessModeling of ultrafast X-ray induced magnetization dynamics in magnetic multilayer systems
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.
- 1 June 2022
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 128 (22) , 223203
Delayed Onset and Directionality of X-Ray-Induced Atomic Displacements Observed on Subatomic Length Scales
Transient structural changes of on subatomic length scales following irradiation with an intense x-ray laser pulse (photon energy: 8.70 keV; pulse duration: 6 fs; fluence: ) 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 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.- 1 June 2022
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 128 (22) , 223203
Delayed Onset and Directionality of X-Ray-Induced Atomic Displacements Observed on Subatomic Length Scales
Transient structural changes of on subatomic length scales following irradiation with an intense x-ray laser pulse (photon energy: 8.70 keV; pulse duration: 6 fs; fluence: ) 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 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.