1
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Brooks NJ, Dorney KM, Ellis J, Denton AE, Gentry C, Ryan SA, Nguyen QLD, Morrill DW, Kapteyn HC, Murnane MM. High-harmonic spin-shearing interferometry for spatially resolved EUV magneto-optical spectroscopy. OPTICS EXPRESS 2024; 32:19076-19087. [PMID: 38859051 DOI: 10.1364/oe.521669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 04/30/2024] [Indexed: 06/12/2024]
Abstract
We present a method for achieving hyperspectral magnetic imaging in the extreme ultraviolet (EUV) region based on high-harmonic generation (HHG). By interfering two mutually coherent orthogonally-polarized and laterally-sheared HHG sources, we create an EUV illumination beam with spatially-dependent ellipticity. By placing a magnetic sample in the beamline and sweeping the relative time delay between the two sources, we record a spatially resolved interferogram that is sensitive to the EUV magnetic circular dichroism of the sample. This image contains the spatially-resolved magneto-optical response of the sample at each harmonic order, and can be used to measure the magnetic properties of spatially inhomogeneous magnetic samples.
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2
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Pankratova M, Miranda IP, Thonig D, Pereiro M, Sjöqvist E, Delin A, Scheid P, Eriksson O, Bergman A. Coupled atomistic spin-lattice simulations of ultrafast demagnetization in 3d ferromagnets. Sci Rep 2024; 14:8138. [PMID: 38584162 PMCID: PMC10999457 DOI: 10.1038/s41598-024-58662-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Accepted: 04/02/2024] [Indexed: 04/09/2024] Open
Abstract
Despite decades of research, the role of the lattice and its coupling to the magnetisation during ultrafast demagnetisation processes is still not fully understood. Here we report on studies of both explicit and implicit lattice effects on laser induced ultrafast demagnetisation of bcc Fe and fcc Co. We do this using atomistic spin- and lattice dynamics simulations following a heat-conserving three-temperature model. We show that this type of Langevin-based simulation is able to reproduce observed trends of the ultrafast magnetization dynamics of fcc Co and bcc Fe. The parameters used in our models are all obtained from electronic structure theory, with the exception of the lattice dynamics damping term, where a range of parameters were investigated. It was found that while the explicit spin-lattice coupling in the studied systems does not impact the demagnetisation process notably, the lattice damping has a large influence on the details of the magnetization dynamics. The dynamics of Fe and Co following the absorption of a femtosecond laser pulse are compared with previous results for Ni and similarities and differences in the materials' behavior are analysed. For all elements investigated so far with this model, we obtain a linear relationship between the value of the maximally demagnetized state and the fluence of the laser pulse , which is in agreement with experiments. Moreover, we demonstrate that the demagnetization amplitude is largest for Ni and smallest for Co. This holds over a wide range of the reported electron-phonon couplings, and this demagnetization trend is in agreement with recent experiments.
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Affiliation(s)
- M Pankratova
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden.
| | - I P Miranda
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden.
| | - D Thonig
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
- School of Science and Technology, Örebro University, 701 82, Örebro, Sweden
| | - M Pereiro
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
| | - E Sjöqvist
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
| | - A Delin
- Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, AlbaNova University Center, 10691, Stockholm, Sweden
- Swedish e-Science Research Center (SeRC), KTH Royal Institute of Technology, 10044, Stockholm, Sweden
- Wallenberg Initiative Materials Science for Sustainability (WISE), KTH Royal Institute of Technology, 10044, Stockholm, Sweden
| | - P Scheid
- LPCT, CNRS, UMR 7019, BP 70239, Université de Lorraine, 54506, Vandoeuvre-lés-Nancy Cedex, France
- IJL, CNRS, UMR 7198, BP 70239, Université de Lorraine, 54000, Nancy Cedex, France
| | - O Eriksson
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
- Wallenberg Initiative Materials Science for Sustainability, Uppsala University, 75121, Uppsala, Sweden
| | - A Bergman
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
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3
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Lu X, Lin Z, Pi H, Zhang T, Li G, Gong Y, Yan Y, Ruan X, Li Y, Zhang H, Li L, He L, Wu J, Zhang R, Weng H, Zeng C, Xu Y. Ultrafast magnetization enhancement via the dynamic spin-filter effect of type-II Weyl nodes in a kagome ferromagnet. Nat Commun 2024; 15:2410. [PMID: 38499551 PMCID: PMC10948858 DOI: 10.1038/s41467-024-46604-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 02/21/2024] [Indexed: 03/20/2024] Open
Abstract
The magnetic type-II Weyl semimetal (MWSM) Co3Sn2S2 has recently been found to host a variety of remarkable phenomena including surface Fermi-arcs, giant anomalous Hall effect, and negative flat band magnetism. However, the dynamic magnetic properties remain relatively unexplored. Here, we investigate the ultrafast spin dynamics of Co3Sn2S2 crystal using time-resolved magneto-optical Kerr effect and reflectivity spectroscopies. We observe a transient magnetization behavior, consisting of spin-flipping dominated fast demagnetization, slow demagnetization due to overall half-metallic electronic structures, and an unexpected ultrafast magnetization enhancement lasting hundreds of picoseconds upon femtosecond laser excitation. By combining temperature-, pump fluence-, and pump polarization-dependent measurements, we unambiguously demonstrate the correlation between the ultrafast magnetization enhancement and the Weyl nodes. Our theoretical modelling suggests that the excited electrons are spin-polarized when relaxing, leading to the enhanced spin-up density of states near the Fermi level and the consequently unusual magnetization enhancement. Our results reveal the unique role of the Weyl properties of Co3Sn2S2 in femtosecond laser-induced spin dynamics.
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Affiliation(s)
- Xianyang Lu
- School of Integrated Circuits, Nanjing University, Suzhou, 215163, China
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Zhiyong Lin
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Hanqi Pi
- Beijing National Research Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Science, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Tan Zhang
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, 19104-6323, USA
| | - Guanqi Li
- School of Integrated Circuits, Guangdong University of Technology, Guangzhou, 510006, China
| | - Yuting Gong
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Yu Yan
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Xuezhong Ruan
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Yao Li
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Hui Zhang
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Lin Li
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Liang He
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Jing Wu
- School of Integrated Circuits, Guangdong University of Technology, Guangzhou, 510006, China.
- York-Nanjing International Joint Center in Spintronics, School of Physics, Engineering and Technology, University of York, York, YO10 5DD, UK.
| | - Rong Zhang
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Hongming Weng
- Beijing National Research Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
- School of Physical Science, University of Chinese Academy of Sciences, Beijing, 100049, China.
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China.
| | - Changgan Zeng
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China.
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China.
| | - Yongbing Xu
- School of Integrated Circuits, Nanjing University, Suzhou, 215163, China.
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China.
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China.
- York-Nanjing International Joint Center in Spintronics, School of Physics, Engineering and Technology, University of York, York, YO10 5DD, UK.
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4
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Shokeen V, Heber M, Kutnyakhov D, Wang X, Yaroslavtsev A, Maldonado P, Berritta M, Wind N, Wenthaus L, Pressacco F, Min CH, Nissen M, Mahatha SK, Dziarzhytski S, Oppeneer PM, Rossnagel K, Elmers HJ, Schönhense G, Dürr HA. Real-time observation of non-equilibrium phonon-electron energy and angular momentum flow in laser-heated nickel. SCIENCE ADVANCES 2024; 10:eadj2407. [PMID: 38295169 PMCID: PMC10830112 DOI: 10.1126/sciadv.adj2407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Accepted: 12/29/2023] [Indexed: 02/02/2024]
Abstract
Identifying the microscopic nature of non-equilibrium energy transfer mechanisms among electronic, spin, and lattice degrees of freedom is central to understanding ultrafast phenomena such as manipulating magnetism on the femtosecond timescale. Here, we use time- and angle-resolved photoemission spectroscopy to go beyond the often-used ensemble-averaged view of non-equilibrium dynamics in terms of quasiparticle temperature evolutions. We show for ferromagnetic Ni that the non-equilibrium electron and spin dynamics display pronounced variations with electron momentum, whereas the magnetic exchange interaction remains isotropic. This highlights the influence of lattice-mediated scattering processes and opens a pathway toward unraveling the still elusive microscopic mechanism of spin-lattice angular momentum transfer.
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Affiliation(s)
- Vishal Shokeen
- Department of Physics and Astronomy, Uppsala University, 751 20 Uppsala, Sweden
| | - Michael Heber
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | | | - Xiaocui Wang
- Department of Physics and Astronomy, Uppsala University, 751 20 Uppsala, Sweden
| | | | - Pablo Maldonado
- Department of Physics and Astronomy, Uppsala University, 751 20 Uppsala, Sweden
| | - Marco Berritta
- Department of Physics and Astronomy, Uppsala University, 751 20 Uppsala, Sweden
| | - Nils Wind
- Institut für Experimentalphysik, Universität Hamburg, 22761 Hamburg, Germany
- Ruprecht Haensel Laboratory, Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Lukas Wenthaus
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | | | - Chul-Hee Min
- Ruprecht Haensel Laboratory, Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Matz Nissen
- Institut für Experimentalphysik, Universität Hamburg, 22761 Hamburg, Germany
| | - Sanjoy K. Mahatha
- Ruprecht Haensel Laboratory, Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | | | - Peter M. Oppeneer
- Department of Physics and Astronomy, Uppsala University, 751 20 Uppsala, Sweden
| | - Kai Rossnagel
- Ruprecht Haensel Laboratory, Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Hans-Joachim Elmers
- Institut für Physik, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany
| | - Gerd Schönhense
- Institut für Physik, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany
| | - Hermann A. Dürr
- Department of Physics and Astronomy, Uppsala University, 751 20 Uppsala, Sweden
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5
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Chen Z, Luo JW, Wang LW. Light-induced ultrafast spin transport in multilayer metallic films originates from sp- d spin exchange coupling. SCIENCE ADVANCES 2023; 9:eadi1618. [PMID: 38100591 PMCID: PMC10848703 DOI: 10.1126/sciadv.adi1618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 11/15/2023] [Indexed: 12/17/2023]
Abstract
Ultrafast interaction between the femtosecond laser pulse and the magnetic metal provides an efficient way to manipulate the magnetic states of matter. Numerous experimental advancements have been made on multilayer metallic films in the last two decades. However, the underlying physics remains unclear. Here, relying on an efficient ab initio spin dynamics simulation algorithm, we revealed the physics that can unify the progress in different experiments. We found that light-induced ultrafast spin transport in multilayer metallic films originates from the sp-d spin-exchange interaction, which can induce an ultrafast, large, and pure spin current from ferromagnetic metal to nonmagnetic metal without charge carrier transport. The resulting trends of spin demagnetization and spin flow are consistent with most experiments. It can explain a variety of ultrafast light-spin manipulation experiments with different systems and different pump-probe technologies, covering a wide range of work in this field.
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Affiliation(s)
- Zhanghui Chen
- Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
- Materials Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Mail Stop 50F, Berkeley, CA 94720, USA
- University of Chinese Academy of Sciences, No.1 Yanqihu East Rd, Huairou District, Beijing 101408, China
| | - Jun-Wei Luo
- Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
- University of Chinese Academy of Sciences, No.1 Yanqihu East Rd, Huairou District, Beijing 101408, China
| | - Lin-Wang Wang
- Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
- Materials Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Mail Stop 50F, Berkeley, CA 94720, USA
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6
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Barhoumi M, Liu J, Lefkidis G, Hübner W. Laser-induced ultrafast spin-transfer processes in non-linear zigzag carbon chain systems. Phys Chem Chem Phys 2023; 25:24563-24580. [PMID: 37661835 DOI: 10.1039/d3cp02483k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
We combine the high-level quantum chemistry theory CCSD and EOM-CCSD together with local and global Λ processes to investigate the details of the laser-induced ultrafast spin manipulation scenarios in non-linear zigzag carbon chain systems Ni2@C32H32 and Ni2@C36H36. The spin density distribution, which is calculated on each many-body state using a Mulliken population analysis, fulfills the requirements to accomplish the spin dynamics processes. Various spin-flip and spin-transfer scenarios are accomplished. All the spin-dynamics processes can be achieved within subpicosecond times. Under the influence of a magnetic field, we find that the spin-transfer scenarios are preserved, while the local spin-flip scenario on a Ni atom can be significantly inhibited depending on the strength of the magnetic field. The impact of the propagation direction of the laser pulse on the spin dynamics processes by varying their polar and azimuthal angles in spherical coordinates is investigated. Additionally, we find that double laser pulses successfully induce the spin-transfer processes. Our outcomes underline the significant potential of carbon chain systems as building blocks for developing future all-optical integrated logic processing units.
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Affiliation(s)
- Mohamed Barhoumi
- Department of Physics, Rheinland-Pfälzische Technische Universität Kaiserslautern (RPTU) Kaiserslautern-Landau, P.O. Box 3049, 67653 Kaiserslautern, Germany.
| | - Jing Liu
- Institute of Theoretical Chemistry, Ulm University, 89081 Ulm, Germany
| | - Georgios Lefkidis
- Department of Physics, Rheinland-Pfälzische Technische Universität Kaiserslautern (RPTU) Kaiserslautern-Landau, P.O. Box 3049, 67653 Kaiserslautern, Germany.
| | - Wolfgang Hübner
- Department of Physics, Rheinland-Pfälzische Technische Universität Kaiserslautern (RPTU) Kaiserslautern-Landau, P.O. Box 3049, 67653 Kaiserslautern, Germany.
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7
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Xie Z, Cai Y, Tang M, Zhou J, Liu J, Peng J, Jiang T, Shi Z, Chen Z. Fluence and Temperature Dependences of Laser-Induced Ultrafast Demagnetization and Recovery Dynamics in L1 0-FePt Thin Film. MATERIALS (BASEL, SWITZERLAND) 2023; 16:5086. [PMID: 37512360 PMCID: PMC10385860 DOI: 10.3390/ma16145086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 07/08/2023] [Accepted: 07/17/2023] [Indexed: 07/30/2023]
Abstract
The fundamental mechanisms of ultrafast demagnetization and magnetization recovery processes in ferromagnetic materials remain incompletely understood. The investigation of different dynamic features which depend on various physical quantities requires a more systematic approach. Here, the femtosecond laser-induced demagnetization and recovery dynamics in L10-Fe0.5Pt0.5 alloy film are studied by utilizing time-resolved magneto-optical Kerr measurements, focusing on their dependences of excitation fluence and ambient temperature over broad ranges. Ultrafast demagnetization dominated by Elliott-Yafet spin-flip scattering, and two-step magnetization recovery processes are found to be involved in all observations. The fast recovery time corresponding to spin-lattice relaxation is much shorter than that of many ferromagnets and increase with excitation fluence. These can be ascribed to the strong spin-orbit coupling (SOC) demonstrated in FePt and the reduction of transient magnetic anisotropy, respectively. Surprisingly, the demagnetization time exhibits no discernible correlation with ambient temperature. Two competitive factors are proposed to account for this phenomenon. On the other hand, the spin-lattice relaxation accelerates as temperature decreases due to enhanced SOC at lower ambient temperature. A semiquantitative analysis is given to get a visualized understanding. These results offer a comprehensive understanding of the dynamic characteristics of ultrafast demagnetization and recovery processes in iron-based materials with strong SOC, highlighting the potential for regulating the magnetization recovery process through temperature and laser fluence adjustments.
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Affiliation(s)
- Zhikun Xie
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
- State-Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
| | - Yuanhai Cai
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
| | - Meng Tang
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Jielin Zhou
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
| | - Junhao Liu
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
| | - Jun Peng
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
| | - Tianran Jiang
- State-Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
| | - Zhong Shi
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Zhifeng Chen
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
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8
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Johnsen PC, Ryan SA, Gentry C, Grafov A, Kapteyn H, Murnane M. A beamline for ultrafast extreme ultraviolet magneto-optical spectroscopy in reflection near the shot noise limit. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2023; 94:033001. [PMID: 37012828 DOI: 10.1063/5.0127119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 01/30/2023] [Indexed: 06/19/2023]
Abstract
High harmonic generation (HHG) makes it possible to measure spin and charge dynamics in materials on femtosecond to attosecond timescales. However, the extreme nonlinear nature of the high harmonic process means that intensity fluctuations can limit measurement sensitivity. Here we present a noise-canceled, tabletop high harmonic beamline for time-resolved reflection mode spectroscopy of magnetic materials. We use a reference spectrometer to independently normalize the intensity fluctuations of each harmonic order and eliminate long term drift, allowing us to make spectroscopic measurements near the shot noise limit. These improvements allow us to significantly reduce the integration time required for high signal-to-noise (SNR) measurements of element-specific spin dynamics. Looking forward, improvements in the HHG flux, optical coatings, and grating design can further reduce the acquisition time for high SNR measurements by 1-2 orders of magnitude, enabling dramatically improved sensitivity to spin, charge, and phonon dynamics in magnetic materials.
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Affiliation(s)
- Peter C Johnsen
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309-0440, USA
| | - Sinéad A Ryan
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309-0440, USA
| | - Christian Gentry
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309-0440, USA
| | - Anya Grafov
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309-0440, USA
| | - Henry Kapteyn
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309-0440, USA
| | - Margaret Murnane
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309-0440, USA
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9
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Spin and Orbital Symmetry Breakings Central to the Laser-Induced Ultrafast Demagnetization of Transition Metals. Symmetry (Basel) 2023. [DOI: 10.3390/sym15020457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023] Open
Abstract
The role of spin and orbital rotational symmetry on the laser-induced magnetization dynamics of itinerant-electron ferromagnets was theoretically investigated. The ultrafast demagnetization of transition metals is shown to be the direct consequence of the fundamental breaking of these conservation laws in the electronic system, an effect that is inherent to the nature of spin-orbit and electron-lattice interactions. A comprehensive symmetry analysis is complemented by exact numerical calculations of the time evolution of optically excited ferromagnetic ground states in the framework of a many-body electronic Hamiltonian. Thus, quantitative relations are established between the strength of the interactions that break the rotational symmetries and the time scales that are relevant for the magnetization dynamics.
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10
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Schreck S, Diesen E, Dell'Angela M, Liu C, Weston M, Capotondi F, Ogasawara H, LaRue J, Costantini R, Beye M, Miedema PS, Halldin Stenlid J, Gladh J, Liu B, Wang HY, Perakis F, Cavalca F, Koroidov S, Amann P, Pedersoli E, Naumenko D, Nikolov I, Raimondi L, Abild-Pedersen F, Heinz TF, Voss J, Luntz AC, Nilsson A. Atom-Specific Probing of Electron Dynamics in an Atomic Adsorbate by Time-Resolved X-Ray Spectroscopy. PHYSICAL REVIEW LETTERS 2022; 129:276001. [PMID: 36638285 DOI: 10.1103/physrevlett.129.276001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 06/14/2022] [Accepted: 11/18/2022] [Indexed: 06/17/2023]
Abstract
The electronic excitation occurring on adsorbates at ultrafast timescales from optical lasers that initiate surface chemical reactions is still an open question. Here, we report the ultrafast temporal evolution of x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) of a simple well-known adsorbate prototype system, namely carbon (C) atoms adsorbed on a nickel [Ni(100)] surface, following intense laser optical pumping at 400 nm. We observe ultrafast (∼100 fs) changes in both XAS and XES showing clear signatures of the formation of a hot electron-hole pair distribution on the adsorbate. This is followed by slower changes on a few picoseconds timescale, shown to be consistent with thermalization of the complete C/Ni system. Density functional theory spectrum simulations support this interpretation.
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Affiliation(s)
- Simon Schreck
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
| | - Elias Diesen
- SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | | | - Chang Liu
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
| | - Matthew Weston
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
| | - Flavio Capotondi
- FERMI, Elettra-Sincrotrone Trieste, SS 14-km 163.5, 34149 Basovizza, Trieste, Italy
| | - Hirohito Ogasawara
- SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - Jerry LaRue
- Schmid College of Science and Technology, Chapman University, Orange, California 92866, USA
| | - Roberto Costantini
- CNR-IOM, SS 14-km 163.5, 34149 Basovizza, Trieste, Italy
- Physics Department, University of Trieste, Via Valerio 2, 34127 Trieste, Italy
| | - Martin Beye
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, Hamburg 22607, Germany
| | - Piter S Miedema
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, Hamburg 22607, Germany
| | - Joakim Halldin Stenlid
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
- SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - Jörgen Gladh
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
- SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - Boyang Liu
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
| | - Hsin-Yi Wang
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
| | - Fivos Perakis
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
| | - Filippo Cavalca
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
| | - Sergey Koroidov
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
| | - Peter Amann
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
| | - Emanuele Pedersoli
- FERMI, Elettra-Sincrotrone Trieste, SS 14-km 163.5, 34149 Basovizza, Trieste, Italy
| | - Denys Naumenko
- FERMI, Elettra-Sincrotrone Trieste, SS 14-km 163.5, 34149 Basovizza, Trieste, Italy
| | - Ivaylo Nikolov
- FERMI, Elettra-Sincrotrone Trieste, SS 14-km 163.5, 34149 Basovizza, Trieste, Italy
| | - Lorenzo Raimondi
- FERMI, Elettra-Sincrotrone Trieste, SS 14-km 163.5, 34149 Basovizza, Trieste, Italy
| | - Frank Abild-Pedersen
- SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - Tony F Heinz
- SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Johannes Voss
- SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - Alan C Luntz
- SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - Anders Nilsson
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
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11
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Tauchert SR, Volkov M, Ehberger D, Kazenwadel D, Evers M, Lange H, Donges A, Book A, Kreuzpaintner W, Nowak U, Baum P. Polarized phonons carry angular momentum in ultrafast demagnetization. Nature 2022; 602:73-77. [PMID: 35110761 DOI: 10.1038/s41586-021-04306-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 12/01/2021] [Indexed: 11/10/2022]
Abstract
Magnetic phenomena are ubiquitous in nature and indispensable for modern science and technology, but it is notoriously difficult to change the magnetic order of a material in a rapid way. However, if a thin nickel film is subjected to ultrashort laser pulses, it loses its magnetic order almost completely within femtosecond timescales1. This phenomenon is widespread2-7 and offers opportunities for rapid information processing8-11 or ultrafast spintronics at frequencies approaching those of light8,9,12. Consequently, the physics of ultrafast demagnetization is central to modern materials research1-7,13-28, but a crucial question has remained elusive: if a material loses its magnetization within mere femtoseconds, where is the missing angular momentum in such a short time? Here we use ultrafast electron diffraction to reveal in nickel an almost instantaneous, long-lasting, non-equilibrium population of anisotropic high-frequency phonons that appear within 150-750 fs. The anisotropy plane is perpendicular to the direction of the initial magnetization and the atomic oscillation amplitude is 2 pm. We explain these observations by means of circularly polarized phonons that quickly absorb the angular momentum of the spin system before macroscopic sample rotation. The time that is needed for demagnetization is related to the time it takes to accelerate the atoms. These results provide an atomistic picture of the Einstein-de Haas effect and signify the general importance of polarized phonons for non-equilibrium dynamics and phase transitions.
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Affiliation(s)
- S R Tauchert
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany.,Ludwig-Maximilians-Universität München, Garching, Germany
| | - M Volkov
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany.,Ludwig-Maximilians-Universität München, Garching, Germany
| | - D Ehberger
- Ludwig-Maximilians-Universität München, Garching, Germany
| | - D Kazenwadel
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany
| | - M Evers
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany
| | - H Lange
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany
| | - A Donges
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany
| | - A Book
- Technische Universität München, Physik-Department E21, Garching, Germany
| | - W Kreuzpaintner
- Technische Universität München, Physik-Department E21, Garching, Germany.,Institute of High Energy Physics, Chinese Academy of Sciences (CAS), Beijing, China.,Spallation Neutron Source Science Center, Dongguan, China
| | - U Nowak
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany
| | - P Baum
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany. .,Ludwig-Maximilians-Universität München, Garching, Germany.
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12
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Longitudinal Magneto-Optical Kerr Effect of Nanoporous CoFeB and W/CoFeB/W Thin Films. COATINGS 2022. [DOI: 10.3390/coatings12020115] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Nanoporous Co40Fe40B20 (CoFeB) and sandwich tungsten (W)/CoFeB/W thin films were fabricated via an anodic aluminum oxide (AAO) template-assisted magneto sputtering process. Their thickness-dependent magneto-optical Kerr effect (MOKE) hysteresis loops were investigated for enhanced Kerr rotation. Control of the Kerr null points of the polarized reflected light can be realized via the thicknesses of the CoFeB layers and W layers. Simulation of the thickness-dependent phase difference change by the finite element method reveals the existence of the two Kerr null points for W/CoFeB/W thin films, matching the experimental result very well. However, there are two additional Kerr null points for pure CoFeB thin films according to the simulation by comparing with the experimental result (only one). Theoretical analysis indicates that the different Kerr null points between the experimental result and the simulation are mainly due to the enhanced inner magnetization in the ferromagnetic CoFeB layer with the increased thickness, which is usually omitted in the simulation. Clearly, the introduction of non-ferromagnetic W layers can experimentally regulate the Kerr null points of ferromagnetic thin films. Moreover, construction of W/CoFeB/W sandwich thin films can greatly increase the highest magneto-optical susceptibility and the saturated Kerr rotation angle when compared with CoFeB thin films of the same thickness.
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13
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Zhang Y, Shi X, Guan M, You W, Zhong Y, Kafle TR, Huang Y, Ding H, Bauer M, Rossnagel K, Meng S, Kapteyn HC, Murnane MM. Creation of a novel inverted charge density wave state. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2022; 9:014501. [PMID: 35071692 PMCID: PMC8759797 DOI: 10.1063/4.0000132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Accepted: 12/21/2021] [Indexed: 06/14/2023]
Abstract
Charge density wave (CDW) order is an emergent quantum phase that is characterized by periodic lattice distortion and charge density modulation, often present near superconducting transitions. Here, we uncover a novel inverted CDW state by using a femtosecond laser to coherently reverse the star-of-David lattice distortion in 1T-TaSe2. We track the signature of this novel CDW state using time- and angle-resolved photoemission spectroscopy and the time-dependent density functional theory to validate that it is associated with a unique lattice and charge arrangement never before realized. The dynamic electronic structure further reveals its novel properties that are characterized by an increased density of states near the Fermi level, high metallicity, and altered electron-phonon couplings. Our results demonstrate how ultrafast lasers can be used to create unique states in materials by manipulating charge-lattice orders and couplings.
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Affiliation(s)
- Yingchao Zhang
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Xun Shi
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Mengxue Guan
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Wenjing You
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | | | - Tika R. Kafle
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Yaobo Huang
- Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201204, China
| | - Hong Ding
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Michael Bauer
- Institute of Experimental and Applied Physics, Kiel University, D-24098 Kiel, Germany
| | | | - Sheng Meng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Henry C. Kapteyn
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Margaret M. Murnane
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
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14
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Dürr HA, Ernstorfer R, Siwick BJ. Revealing momentum-dependent electron-phonon and phonon-phonon coupling in complex materials with ultrafast electron diffuse scattering. MRS BULLETIN 2021; 46:731-737. [PMID: 34720390 PMCID: PMC8550364 DOI: 10.1557/s43577-021-00156-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 07/14/2021] [Indexed: 06/13/2023]
Abstract
ABSTRACT Despite their fundamental role in determining many important properties of materials, detailed momentum-dependent information on the strength of electron-phonon and phonon-phonon coupling across the entire Brillouin zone has remained elusive. Ultrafast electron diffuse scattering (UEDS) is a recently developed technique that is making a significant contribution to these questions. Here, we describe both the UEDS methodology and the information content of ultrafast, photoinduced changes in phonon-diffuse scattering from single-crystal materials. We present results obtained from Ni, WSe2, and TiSe2, materials that are characterized by a complex interplay between electronic (charge, spin) and lattice degrees of freedom. We demonstrate the power of this technique by unraveling carrier-phonon and phonon-phonon interactions in both momentum and time and following nonequilibrium phonon dynamics in detail on ultrafast time scales. By combining ab initio calculations with ultrafast diffuse electron scattering, insights into electronic and magnetic dynamics that impact UEDS indirectly can also be obtained.
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Affiliation(s)
- Hermann A. Dürr
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
| | - Ralph Ernstorfer
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Bradley J. Siwick
- Centre for the Physics of Materials, McGill University, 801 Sherbrooke St. W, Montreal, Canada
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15
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Lloyd-Hughes J, Oppeneer PM, Pereira Dos Santos T, Schleife A, Meng S, Sentef MA, Ruggenthaler M, Rubio A, Radu I, Murnane M, Shi X, Kapteyn H, Stadtmüller B, Dani KM, da Jornada FH, Prinz E, Aeschlimann M, Milot RL, Burdanova M, Boland J, Cocker T, Hegmann F. The 2021 ultrafast spectroscopic probes of condensed matter roadmap. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:353001. [PMID: 33951618 DOI: 10.1088/1361-648x/abfe21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 05/05/2021] [Indexed: 06/12/2023]
Abstract
In the 60 years since the invention of the laser, the scientific community has developed numerous fields of research based on these bright, coherent light sources, including the areas of imaging, spectroscopy, materials processing and communications. Ultrafast spectroscopy and imaging techniques are at the forefront of research into the light-matter interaction at the shortest times accessible to experiments, ranging from a few attoseconds to nanoseconds. Light pulses provide a crucial probe of the dynamical motion of charges, spins, and atoms on picosecond, femtosecond, and down to attosecond timescales, none of which are accessible even with the fastest electronic devices. Furthermore, strong light pulses can drive materials into unusual phases, with exotic properties. In this roadmap we describe the current state-of-the-art in experimental and theoretical studies of condensed matter using ultrafast probes. In each contribution, the authors also use their extensive knowledge to highlight challenges and predict future trends.
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Affiliation(s)
- J Lloyd-Hughes
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - P M Oppeneer
- Department of Physics and Astronomy, Uppsala University, PO Box 516, S-75120 Uppsala, Sweden
| | - T Pereira Dos Santos
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
| | - A Schleife
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
- Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
- National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
| | - S Meng
- Institute of Physics, Chinese Academy of Sciences, Beijing, People's Republic of China
| | - M A Sentef
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science (CFEL), 22761 Hamburg, Germany
| | - M Ruggenthaler
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science (CFEL), 22761 Hamburg, Germany
| | - A Rubio
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science (CFEL), 22761 Hamburg, Germany
- Nano-Bio Spectroscopy Group and ETSF, Universidad del País Vasco UPV/EHU 20018 San Sebastián, Spain
- Center for Computational Quantum Physics (CCQ), The Flatiron Institute, 162 Fifth Avenue, New York, NY, 10010, United States of America
| | - I Radu
- Department of Physics, Freie Universität Berlin, Germany
- Max Born Institute, Berlin, Germany
| | - M Murnane
- JILA, University of Colorado and NIST, Boulder, CO, United States of America
| | - X Shi
- JILA, University of Colorado and NIST, Boulder, CO, United States of America
| | - H Kapteyn
- JILA, University of Colorado and NIST, Boulder, CO, United States of America
| | - B Stadtmüller
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - K M Dani
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Japan
| | - F H da Jornada
- Department of Materials Science and Engineering, Stanford University, Stanford, 94305, CA, United States of America
| | - E Prinz
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - M Aeschlimann
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - R L Milot
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - M Burdanova
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - J Boland
- Photon Science Institute, Department of Electrical and Electronic Engineering, University of Manchester, United Kingdom
| | - T Cocker
- Michigan State University, United States of America
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16
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Chardonnet V, Hennes M, Jarrier R, Delaunay R, Jaouen N, Kuhlmann M, Ekanayake N, Léveillé C, von Korff Schmising C, Schick D, Yao K, Liu X, Chiuzbăian GS, Lüning J, Vodungbo B, Jal E. Toward ultrafast magnetic depth profiling using time-resolved x-ray resonant magnetic reflectivity. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2021; 8:034305. [PMID: 34235231 PMCID: PMC8225393 DOI: 10.1063/4.0000109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 06/01/2021] [Indexed: 06/13/2023]
Abstract
During the last two decades, a variety of models have been developed to explain the ultrafast quenching of magnetization following femtosecond optical excitation. These models can be classified into two broad categories, relying either on a local or a non-local transfer of angular momentum. The acquisition of the magnetic depth profiles with femtosecond resolution, using time-resolved x-ray resonant magnetic reflectivity, can distinguish local and non-local effects. Here, we demonstrate the feasibility of this technique in a pump-probe geometry using a custom-built reflectometer at the FLASH2 free-electron laser (FEL). Although FLASH2 is limited to the production of photons with a fundamental wavelength of 4 nm ( ≃ 310 eV ), we were able to probe close to the Fe L 3 edge ( 706.8 eV ) of a magnetic thin film employing the third harmonic of the FEL. Our approach allows us to extract structural and magnetic asymmetry signals revealing two dynamics on different time scales which underpin a non-homogeneous loss of magnetization and a significant dilation of 2 Å of the layer thickness followed by oscillations. Future analysis of the data will pave the way to a full quantitative description of the transient magnetic depth profile combining femtosecond with nanometer resolution, which will provide further insight into the microscopic mechanisms underlying ultrafast demagnetization.
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Affiliation(s)
- Valentin Chardonnet
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Marcel Hennes
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Romain Jarrier
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Renaud Delaunay
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Nicolas Jaouen
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, B.P. 48, 91192 Gif-sur-Yvette, France
| | | | | | - Cyril Léveillé
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, B.P. 48, 91192 Gif-sur-Yvette, France
| | | | - Daniel Schick
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany
| | - Kelvin Yao
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany
| | - Xuan Liu
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, B.P. 48, 91192 Gif-sur-Yvette, France
| | - Gheorghe S. Chiuzbăian
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Jan Lüning
- Helmholtz-Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany
| | - Boris Vodungbo
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Emmanuelle Jal
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
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17
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Mattern M, Pudell JE, Laskin G, von Reppert A, Bargheer M. Analysis of the temperature- and fluence-dependent magnetic stress in laser-excited SrRuO 3. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2021; 8:024302. [PMID: 33786338 PMCID: PMC7994007 DOI: 10.1063/4.0000072] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 02/23/2021] [Indexed: 06/07/2023]
Abstract
We use ultrafast x-ray diffraction to investigate the effect of expansive phononic and contractive magnetic stress driving the picosecond strain response of a metallic perovskite SrRuO3 thin film upon femtosecond laser excitation. We exemplify how the anisotropic bulk equilibrium thermal expansion can be used to predict the response of the thin film to ultrafast deposition of energy. It is key to consider that the laterally homogeneous laser excitation changes the strain response compared to the near-equilibrium thermal expansion because the balanced in-plane stresses suppress the Poisson stress on the picosecond timescale. We find a very large negative Grüneisen constant describing the large contractive stress imposed by a small amount of energy in the spin system. The temperature and fluence dependence of the strain response for a double-pulse excitation scheme demonstrates the saturation of the magnetic stress in the high-fluence regime.
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Affiliation(s)
- M. Mattern
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | | | - G. Laskin
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - A. von Reppert
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | - M. Bargheer
- Author to whom correspondence should be addressed:. URL:http://www.uni-potsdam.de/udkm
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18
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Time-Resolved XUV Absorption Spectroscopy and Magnetic Circular Dichroism at the Ni M2,3-Edges. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app11010325] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Ultrashort optical pulses can trigger a variety of non-equilibrium processes in magnetic thin films affecting electrons and spins on femtosecond timescales. In order to probe the charge and magnetic degrees of freedom simultaneously, we developed an X-ray streaking technique that has the advantage of providing a jitter-free picture of absorption cross-section changes. In this paper, we present an experiment based on this approach, which we performed using five photon probing energies at the Ni M2,3-edges. This allowed us to retrieve the absorption and magnetic circular dichroism time traces, yielding detailed information on transient modifications of electron and spin populations close to the Fermi level. Our findings suggest that the observed absorption and magnetic circular dichroism dynamics both depend on the extreme ultraviolet (XUV) probing wavelength, and can be described, at least qualitatively, by assuming ultrafast energy shifts of the electronic and magnetic elemental absorption resonances, as reported in recent work. However, our analysis also hints at more complex changes, highlighting the need for further experimental and theoretical studies in order to gain a thorough understanding of the interplay of electronic and spin degrees of freedom in optically excited magnetic thin films.
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19
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Acharya SR, Turkowski V, Zhang GP, Rahman TS. Ultrafast Electron Correlations and Memory Effects at Work: Femtosecond Demagnetization in Ni. PHYSICAL REVIEW LETTERS 2020; 125:017202. [PMID: 32678622 DOI: 10.1103/physrevlett.125.017202] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 05/04/2020] [Accepted: 06/01/2020] [Indexed: 06/11/2023]
Abstract
Experimental observations of the ultrafast (less than 50 fs) demagnetization of Ni have so far defied theoretical explanations particularly since its spin-flipping time is much less than that resulting from spin-orbit and electron-lattice interactions. Through the application of an approach that benefits from spin-flip time-dependent density-functional theory and dynamical mean-field theory, we show that proper inclusion of electron correlations and memory (time dependence of electron-electron interaction) effects leads to demagnetization at the femtosecond scale, in good agreement with experimental observations. Furthermore, our calculations reveal that this ultrafast demagnetization results mainly from spin-flip transitions from occupied to unoccupied orbitals implying a dynamical reduction of exchange splitting. These conclusions are found to be valid for a wide range of laser pulse amplitudes. They also pave the way for ab initio investigations of ultrafast charge and spin dynamics in a variety of quantum materials in which electron correlations may play a definitive role.
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Affiliation(s)
- Shree Ram Acharya
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - Volodymyr Turkowski
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
| | - G P Zhang
- Department of Physics, Indiana State University, Terre Haute, Indiana 47809, USA
| | - Talat S Rahman
- Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
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20
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Femtosecond X-ray induced changes of the electronic and magnetic response of solids from electron redistribution. Nat Commun 2019; 10:5289. [PMID: 31754109 PMCID: PMC6872582 DOI: 10.1038/s41467-019-13272-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 10/24/2019] [Indexed: 11/08/2022] Open
Abstract
Resonant X-ray absorption, where an X-ray photon excites a core electron into an unoccupied valence state, is an essential process in many standard X-ray spectroscopies. With increasing X-ray intensity, the X-ray absorption strength is expected to become nonlinear. Here, we report the onset of such a nonlinearity in the resonant X-ray absorption of magnetic Co/Pd multilayers near the Co L[Formula: see text] edge. The nonlinearity is directly observed through the change of the absorption spectrum, which is modified in less than 40 fs within 2 eV of its threshold. This is interpreted as a redistribution of valence electrons near the Fermi level. For our magnetic sample this also involves mixing of majority and minority spins, due to sample demagnetization. Our findings reveal that nonlinear X-ray responses of materials may already occur at relatively low intensities, where the macroscopic sample is not destroyed, providing insight into ultrafast charge and spin dynamics.
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21
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Murnane MM, Ye J. Coherent light brightens the quantum science frontier. PHYSICS TODAY 2019; 72:10.1063/pt.3.4140. [PMID: 33299256 PMCID: PMC7722474 DOI: 10.1063/pt.3.4140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Controlling coherent light across a vast spectral range enables ultraprecise measurements and the quantum control of atomic, molecular, and condensed-matter systems.
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22
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Sánchez-Barriga J, Ovsyannikov R, Fink J. Strong Spin Dependence of Correlation Effects in Ni Due to Stoner Excitations. PHYSICAL REVIEW LETTERS 2018; 121:267201. [PMID: 30636126 DOI: 10.1103/physrevlett.121.267201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Indexed: 06/09/2023]
Abstract
Using high-resolution angle-resolved photoemission, we observe a strong spin-dependent renormalization and lifetime broadening of the quasiparticle excitations in the electronic band structure of Ni(111) in an energy window of ∼0.3 eV below the Fermi level. We derive a quantitative result for the spin-dependent lifetime broadening by comparing the scattering rates of majority and minority d states, and further show that spin-dependent electron correlations are instead negligible for sp states. From our analysis we experimentally determine the effective on-site Coulomb interaction U caused by Stoner-like interband transitions between majority and minority d states. The present results demonstrate the remarkable impact of spin-dependent electron correlation effects originating from single-particle excitations in a prototypical 3d transition metal, paving the way for further refinement of current many-body theoretical approaches.
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Affiliation(s)
- J Sánchez-Barriga
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - R Ovsyannikov
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - J Fink
- Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstrasse 20, D-01069 Dresden, Germany
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzerstrasse 40, D-01187 Dresden, Germany
- Institut für Festkörperphysik, Technische Universität Dresden, D-01062 Dresden, Germany
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