1
|
Wu N, Zhang S, Chen D, Wang Y, Meng S. Three-stage ultrafast demagnetization dynamics in a monolayer ferromagnet. Nat Commun 2024; 15:2804. [PMID: 38555344 PMCID: PMC10981666 DOI: 10.1038/s41467-024-47128-4] [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: 07/15/2023] [Accepted: 03/21/2024] [Indexed: 04/02/2024] Open
Abstract
Intense laser pulses can be used to demagnetize a magnetic material on an extremely short timescale. While this ultrafast demagnetization offers the potential for new magneto-optical devices, it poses challenges in capturing coupled spin-electron and spin-lattice dynamics. In this article, we study the photoinduced ultrafast demagnetization of a prototype monolayer ferromagnet Fe3GeTe2 and resolve the three-stage demagnetization process characterized by an ultrafast and substantial demagnetization on a timescale of 100 fs, followed by light-induced coherent A1g phonon dynamics which is strongly coupled to the spin dynamics in the next 200-800 fs. In the third stage, chiral lattice vibrations driven by nonlinear phonon couplings, both in-plane and out-of-plane are produced, resulting in significant spin precession. Nonadiabatic effects are found to introduce considerable phonon hardening and suppress the spin-lattice couplings during demagnetization. Our results advance our understanding of dynamic charge-spin-lattice couplings in the ultrafast demagnetization and evidence angular momentum transfer between the phonon and spin degrees of freedom.
Collapse
Affiliation(s)
- Na Wu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Shengjie Zhang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Daqiang Chen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Yaxian Wang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
| | - Sheng Meng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China.
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China.
| |
Collapse
|
2
|
Lyu P, Sødequist J, Sheng X, Qiu Z, Tadich A, Li Q, Edmonds MT, Zhao M, Redondo J, Švec M, Song P, Olsen T, Lu J. Gate-Tunable Renormalization of Spin-Correlated Flat-Band States and Bandgap in a 2D Magnetic Insulator. ACS NANO 2023; 17:15441-15448. [PMID: 37552585 DOI: 10.1021/acsnano.3c01038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/10/2023]
Abstract
Emergent quantum phenomena in two-dimensional van der Waal (vdW) magnets are largely governed by the interplay between exchange and Coulomb interactions. The ability to precisely tune the Coulomb interaction enables the control of spin-correlated flat-band states, band gap, and unconventional magnetism in such strongly correlated materials. Here, we demonstrate a gate-tunable renormalization of spin-correlated flat-band states and bandgap in magnetic chromium tribromide (CrBr3) monolayers grown on graphene. Our gate-dependent scanning tunneling spectroscopy (STS) studies reveal that the interflat-band spacing and bandgap of CrBr3 can be continuously tuned by 120 and 240 meV, respectively, via electrostatic injection of carriers into the hybrid CrBr3/graphene system. This can be attributed to the self-screening of CrBr3 arising from the gate-induced carriers injected into CrBr3, which dominates over the weakened remote screening of the graphene substrate due to the decreased carrier density in graphene. Precise tuning of the spin-correlated flat-band states and bandgap in 2D magnets via electrostatic modulation of Coulomb interactions not only provides effective strategies for optimizing the spin transport channels but also may exert a crucial influence on the exchange energy and spin-wave gap, which could raise the critical temperature for magnetic order.
Collapse
Affiliation(s)
- Pin Lyu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117544, Singapore
| | - Joachim Sødequist
- Department of Physics, Computational Atomic-Scale Materials Design (CAMD), Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Xiaoyu Sheng
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Zhizhan Qiu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117544, Singapore
| | - Anton Tadich
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria 3800, Australia
- Australian Synchrotron, Clayton, Victoria 3168, Australia
| | - Qile Li
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria 3800, Australia
- School of Physics and Astronomy, Monash University, Clayton, Victoria 3800, Australia
| | - Mark T Edmonds
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria 3800, Australia
- School of Physics and Astronomy, Monash University, Clayton, Victoria 3800, Australia
| | - Meng Zhao
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Jesús Redondo
- Institute of Physics of the Czech Academy of Sciences, Cukrovarnicka 10, 162 00 Prague 6, Czech Republic
- Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague, Czech Republic
| | - Martin Švec
- Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague, Czech Republic
| | - Peng Song
- School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798,Singapore
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798,Singapore
| | - Thomas Olsen
- Department of Physics, Computational Atomic-Scale Materials Design (CAMD), Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Jiong Lu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117544, Singapore
| |
Collapse
|
3
|
Bonini J, Ren S, Vanderbilt D, Stengel M, Dreyer CE, Coh S. Frequency Splitting of Chiral Phonons from Broken Time-Reversal Symmetry in CrI_{3}. PHYSICAL REVIEW LETTERS 2023; 130:086701. [PMID: 36898102 DOI: 10.1103/physrevlett.130.086701] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 01/19/2023] [Indexed: 06/18/2023]
Abstract
Conventional approaches for lattice dynamics based on static interatomic forces do not fully account for the effects of time-reversal-symmetry breaking in magnetic systems. Recent approaches to rectify this involve incorporating the first-order change in forces with atomic velocities under the assumption of adiabatic separation of electronic and nuclear degrees of freedom. In this Letter, we develop a first-principles method to calculate this velocity-force coupling in extended solids and show via the example of ferromagnetic CrI_{3} that, due to the slow dynamics of the spins in the system, the assumption of adiabatic separation can result in large errors for splittings of zone-center chiral modes. We demonstrate that an accurate description of the lattice dynamics requires treating magnons and phonons on the same footing.
Collapse
Affiliation(s)
- John Bonini
- Center for Computational Quantum Physics, Flatiron Institute, 162 5th Avenue, New York, New York 10010, USA
| | - Shang Ren
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08845-0849, USA
| | - David Vanderbilt
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08845-0849, USA
| | - Massimiliano Stengel
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain
| | - Cyrus E Dreyer
- Center for Computational Quantum Physics, Flatiron Institute, 162 5th Avenue, New York, New York 10010, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800, USA
| | - Sinisa Coh
- Materials Science and Mechanical Engineering, University of California, Riverside, California 92521, USA
| |
Collapse
|
4
|
Han X, You JY, Wu S, Li R, Feng YP, Loh KP, Zhao X. Atomically Unveiling an Atlas of Polytypes in Transition-Metal Trihalides. J Am Chem Soc 2023; 145:3624-3635. [PMID: 36735914 DOI: 10.1021/jacs.2c12801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Transition-metal trihalides MX3 (M = Cr, Ru; X = Cl, Br, and I) belong to a family of novel two-dimensional (2D) magnets that can exhibit topological magnons and electromagnetic properties, thus affording great promises in next-generation spintronic devices. Rich magnetic ground states observed in the MX3 family are believed to be strongly correlated to the signature Kagome lattice and interlayer van der Waals coupling raised from distinct stacking orders. However, the intrinsic air instability of MX3 makes their direct atomic-scale analysis challenging. Therefore, information on the stacking-registry-dependent magnetism for MX3 remains elusive, which greatly hinders the engineering of desired phases. Here, we report a nondestructive transfer method and successfully realize an intact transfer of bilayer MX3, as evidenced by scanning transmission electron microscopy (STEM). After surveying hundreds of MX3 thin flakes, we provide a full spectrum of stacking orders in MX3 with atomic precision and calculated their associated magnetic ground states, unveiled by combined STEM and density functional theory (DFT). In addition to well-documented phases, we discover a new monoclinic C2/c phase in the antiferromagnetic (AFM) structure widely existing in MX3. Rich stacking polytypes, including C2/c, C2/m, R3̅, P3112, etc., provide rich and distinct magnetic ground states in MX3. Besides, a high density of strain soliton boundaries is consistently found in all MX3, combined with likely inverted structures, allowing AFM to ferromagnetic (FM) transitions in most MX3. Therefore, our study sheds light on the structural basis of diverse magnetic orders in MX3, paving the way for modulating magnetic couplings via stacking engineering.
Collapse
Affiliation(s)
- Xiaocang Han
- School of Materials Science and Engineering, Peking University, Beijing100871, China
| | - Jing-Yang You
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551Singapore
| | - Shengqiang Wu
- School of Materials Science and Engineering, Peking University, Beijing100871, China
| | - Runlai Li
- College of Polymer Science & Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu610065, China
| | - Yuan Ping Feng
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551Singapore
| | - Kian Ping Loh
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR, 999077, China
| | - Xiaoxu Zhao
- School of Materials Science and Engineering, Peking University, Beijing100871, China
| |
Collapse
|
5
|
Lis O, Kozlenko D, Kichanov S, Lukin E, Zel I, Savenko B. Structural, Magnetic and Vibrational Properties of Van Der Waals Ferromagnet CrBr 3 at High Pressure. MATERIALS (BASEL, SWITZERLAND) 2023; 16:454. [PMID: 36614792 PMCID: PMC9821824 DOI: 10.3390/ma16010454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 12/29/2022] [Accepted: 12/31/2022] [Indexed: 06/17/2023]
Abstract
The crystal and magnetic structures of van der Waals layered ferromagnet CrBr3 were studied using X-ray powder diffraction and neutron powder diffraction at pressures up to 23 GPa at ambient temperature and up to 2.8 GPa in the temperature range 6-300 K, respectively. The vibration spectra of CrBr3 were studied using Raman spectroscopy at pressures up to 23 GPa at ambient temperature. The anomalous pressure behavior of structural parameters and vibrational modes was observed, associated with a gradual isostructural phase transition in the pressure range 2.5-7 GPa. The Curie temperature TC reduced rapidly with a pressure coefficient dTC/dP=-4.1(4) K/GPa. A full suppression of the ferromagnetic state was expected at PC~8.4 GPa, where onset of the antiferromagnetic spin arrangement or magnetically disordered state may take place. Anomalies in Raman spectra at P~15 GPa point to another possible phase transformation in CrBr3, which may be related to the proximity of metallization of this van der Waals ferromagnet.
Collapse
Affiliation(s)
- Olga Lis
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia
- Department of Nuclear-Physical Materials Science, Institute of Physics, Kazan (Volga Region) Federal University, 420008 Kazan, Russia
| | - Denis Kozlenko
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia
| | - Sergey Kichanov
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia
| | - Evgenii Lukin
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia
| | - Ivan Zel
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia
| | - Boris Savenko
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia
| |
Collapse
|