Showing 1–3 of 3 results for author: Kosyl, K

Laser-induced ultrafast structural transformations in thin Fe layer revealed by time-resolved X-ray diffraction

Authors: O. Liubchenko, J. Antonowicz, K. Sokolowski-Tinten, P. Zalden, R. Minikayev, I. Milov, T. J. Albert, C. Bressler, M. Chojnacki, P. Dłużewski, P. Dzięgielewski, A. Rodriguez-Fernandez, K. Fronc, W. Gawelda, K. Georgarakis, A. L. Greer, I. Jacyna, R. W. E. van de Kruijs, R. Kamiński, D. Khakhulin, D. Klinger, K. Kosyl, K. Kubicek, A. Olczak, N. T. Panagiotopoulos , et al. (5 additional authors not shown)

Abstract: The ultrafast structural response of a thin iron film to sub-ps pulsed laser-induced heating has been investigated using time-resolved X-ray diffraction in the partial melting regime. A tetragonal distortion of the bcc-phase emerges at ~6 ps. Its formation is delayed relative to the initial heating (1-2 ps) and partial melting (2-5 ps) of the material, and controlled by the stress release in the q… ▽ More The ultrafast structural response of a thin iron film to sub-ps pulsed laser-induced heating has been investigated using time-resolved X-ray diffraction in the partial melting regime. A tetragonal distortion of the bcc-phase emerges at ~6 ps. Its formation is delayed relative to the initial heating (1-2 ps) and partial melting (2-5 ps) of the material, and controlled by the stress release in the quasi-instantaneously pressurized film. The distortion persists for at least 60 ps indicating the formation of a metastable bct phase between the equilibrium bcc and fcc phases. △ Less

Submitted 8 August, 2025; v1 submitted 23 June, 2025; originally announced June 2025.

Comments: The revised manuscript features an upgraded discussion and conclusion parts, with particular emphasis on the role of stress-release mechanisms. The text has been substantially shortened and refined, with careful language improvements to ensure clarity and precision. Additionally, the manuscript has been formatted in accordance with PRL submission guidelines

Structural pathways for ultrafast melting of optically excited thin polycrystalline Palladium films

Authors: Jerzy Antonowicz, Adam Olczak, Klaus Sokolowski-Tinten, Peter Zalden, Igor Milov, Przemysław Dzięgielewski, Christian Bressler, Henry N. Chapman, Michał Chojnacki, Piotr Dłużewski, Angel Rodriguez-Fernandez, Krzysztof Fronc, Wojciech Gawełda, Konstantinos Georgarakis, Alan L. Greer, Iwanna Jacyna, Robbert W. E. van de Kruijs, Radosław Kamiński, Dmitry Khakhulin, Dorota Klinger, Katarzyna M. Kosyl, Katharina Kubicek, Kirill P. Migdal, Roman Minikayev, Nikolaos T. Panagiotopoulos , et al. (6 additional authors not shown)

Abstract: Due to its extremely short timescale, the non-equilibrium melting of metals is exceptionally difficult to probe experimentally. The knowledge of melting mechanisms is thus based mainly on the results of theoretical predictions. This work reports on the investigation of ultrafast melting of thin polycrystalline Pd films studied by optical laser pump - X-ray free-electron laser probe experiments and… ▽ More Due to its extremely short timescale, the non-equilibrium melting of metals is exceptionally difficult to probe experimentally. The knowledge of melting mechanisms is thus based mainly on the results of theoretical predictions. This work reports on the investigation of ultrafast melting of thin polycrystalline Pd films studied by optical laser pump - X-ray free-electron laser probe experiments and molecular-dynamics simulations. By acquiring X-ray diffraction snapshots with sub-picosecond resolution, we capture the sample's atomic structure during its transition from the crystalline to the liquid state. Bridging the timescales of experiments and simulations allows us to formulate a realistic microscopic picture of melting. We demonstrate that the existing models of strongly non-equilibrium melting, developed for systems with relatively weak electron-phonon coupling, remain valid even for ultrafast heating rates achieved in femtosecond laser-excited Pd. Furthermore, we highlight the role of pre-existing and transiently generated crystal defects in the transition to the liquid state. △ Less

Submitted 19 September, 2023; originally announced September 2023.

Comments: main manuscript 33 pages, 9 figures; supplemental material 19 pages, 13 figures - all in one file

Orbital-selective Mott phase and spin nematicity in Ni-substituted FeTe$_{0.65}$Se$_{0.35}$ single crystals

Authors: Marta Z. Cieplak, I. Zajcewa, A. Lynnyk, K. M. Kosyl, D. J. Gawryluk

Abstract: The normal state in iron chalcogenides is metallic but highly unusual, with orbital and spin degrees of freedom partially itinerant or localized depending on temperature, leading to many unusual features. In this work, we report on the observations of two of such features, the orbital selective Mott phase (OSMP) and spin nematicity, evidenced in magnetization and magnetotransport [resistivity, Hal… ▽ More The normal state in iron chalcogenides is metallic but highly unusual, with orbital and spin degrees of freedom partially itinerant or localized depending on temperature, leading to many unusual features. In this work, we report on the observations of two of such features, the orbital selective Mott phase (OSMP) and spin nematicity, evidenced in magnetization and magnetotransport [resistivity, Hall effect, anisotropic magnetoresistance (AMR)] of Fe$_{1-y}$Ni$_y$Te$_{0.65}$Se$_{0.35}$ single crystals, with $0 < y < 0.21$. Substitution of Ni dopes crystals with electrons, what eliminates some of the hole pockets from Fermi level, leaving only one, originating from $d_{xy}$ orbital. This leads to electron-dominated conduction at low $T$ for $y \gtrsim 0.06$. However, at high temperatures, $T \gtrsim 125 ÷178$ K, the conduction reverses to hole-dominated. Anomalies in magnetization and resistivity are observed at temperatures which approach high-$T$ boundary of the electron-dominated region. Analysis of these effects suggests a link with the appearance of the $d_{z^2}$ hole pockets at X points of the Brillouin zone in the OSMP phase, facilitated by the localization of $d_{xy}$ orbital, as recently reported by angular resolved photoemission experiments ($\textit{J. Huang et al., Commun. Phys. 5, 29 (2022)}$). The low-$T$ AMR shows mixed 4-fold and 2-fold rotational symmetry of in-plane magnetocrystalline anisotropy, with the 4-fold term the largest at small $y$, and suppressed at intermediate $y$. These results are consistent with the mixed stripe/bicollinear magnetic correlations at small $y$, and suppression of stripe correlations at intermediate $y$, indicating development of spin nematicity with increasing Ni doping, which possibly contributes to the suppression of superconductivity. △ Less

Submitted 4 April, 2024; v1 submitted 28 November, 2022; originally announced November 2022.