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Yang Y, Wang P, Chen J, Zhang D, Pan C, Hu S, Wang T, Yue W, Chen C, Jiang W, Zhu L, Qiu X, Yao Y, Li Y, Wang W, Jiang Y. Orbital torque switching in perpendicularly magnetized materials. Nat Commun 2024; 15:8645. [PMID: 39369005 PMCID: PMC11455943 DOI: 10.1038/s41467-024-52824-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Accepted: 09/23/2024] [Indexed: 10/07/2024] Open
Abstract
The orbital Hall effect in light materials has attracted considerable attention for developing orbitronic devices. Here we investigate the orbital torque efficiency and demonstrate the switching of the perpendicularly magnetized materials through the orbital Hall material, i.e., Zr. The orbital torque efficiency of approximately 0.78 is achieved in the Zr orbital Hall material with the perpendicularly magnetized [Co/Pt]3 sample, which significantly surpasses that of the perpendicularly magnetized CoFeB/Gd/CoFeB sample (approximately 0.04). Such a notable difference is attributed to the different spin-orbit correlation strength between the [Co/Pt]3 sample and the CoFeB/Gd/CoFeB sample, confirmed through theoretical calculations. Furthermore, the full magnetization switching of the [Co/Pt]3 samples with a switching current density of approximately 2.6×106 A/cm2 has been realized through Zr, which even outperforms that of the W spin Hall material. Our finding provides a guideline to understand orbital torque efficiency and paves the way for developing energy-efficient orbitronic devices.
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Affiliation(s)
- Yuhe Yang
- School of Material Science and Engineering, Tiangong University, Tianjin, 300387, China
| | - Ping Wang
- Institute of Quantum Materials and Devices, School of Electronics and Information Engineering, Tiangong University, Tianjin, 300387, China
- Cangzhou Institute of Tiangong University, Cangzhou, 061000, China
| | - Jiali Chen
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China
- Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing, 100081, China
| | - Delin Zhang
- School of Material Science and Engineering, Tiangong University, Tianjin, 300387, China.
- Institute of Quantum Materials and Devices, School of Electronics and Information Engineering, Tiangong University, Tianjin, 300387, China.
- Cangzhou Institute of Tiangong University, Cangzhou, 061000, China.
| | - Chang Pan
- School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Shuai Hu
- Institute of Quantum Materials and Devices, School of Electronics and Information Engineering, Tiangong University, Tianjin, 300387, China
| | - Ting Wang
- School of Material Science and Engineering, Tiangong University, Tianjin, 300387, China
| | - Wensi Yue
- Institute of Quantum Materials and Devices, School of Electronics and Information Engineering, Tiangong University, Tianjin, 300387, China
| | - Cheng Chen
- Institute of Quantum Materials and Devices, School of Electronics and Information Engineering, Tiangong University, Tianjin, 300387, China
| | - Wei Jiang
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China.
- Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing, 100081, China.
| | - Lujun Zhu
- School of Physics and Information Technology, Shaanxi Normal University, Xi'an, 710062, China
| | - Xuepeng Qiu
- School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Yugui Yao
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China
- Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing, 100081, China
| | - Yue Li
- School of Physical Science & Technology, Tiangong University, Tianjin, 300387, China
| | - Wenhong Wang
- School of Material Science and Engineering, Tiangong University, Tianjin, 300387, China
- Institute of Quantum Materials and Devices, School of Electronics and Information Engineering, Tiangong University, Tianjin, 300387, China
- School of Physical Science & Technology, Tiangong University, Tianjin, 300387, China
| | - Yong Jiang
- School of Material Science and Engineering, Tiangong University, Tianjin, 300387, China.
- Institute of Quantum Materials and Devices, School of Electronics and Information Engineering, Tiangong University, Tianjin, 300387, China.
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2
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Lee KJ, Cros V, Lee HW. Electric-field-induced orbital angular momentum in metals. NATURE MATERIALS 2024; 23:1302-1304. [PMID: 39349649 DOI: 10.1038/s41563-024-01978-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2024]
Affiliation(s)
- Kyung-Jin Lee
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
| | - Vincent Cros
- Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - Hyun-Woo Lee
- Department of Physics, Pohang University of Science and Technology, Pohang, Korea.
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3
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Kefayati A, Nikolić BK. Origins of Electromagnetic Radiation from Spintronic Terahertz Emitters: A Time-Dependent Density Functional Theory plus Jefimenko Equations Approach. PHYSICAL REVIEW LETTERS 2024; 133:136704. [PMID: 39392943 DOI: 10.1103/physrevlett.133.136704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Accepted: 08/27/2024] [Indexed: 10/13/2024]
Abstract
Microscopic origins of charge currents and electromagnetic (EM) radiation generated by them in spintronic THz emitters-such as, femtosecond laser pulse-driven single magnetic layer or its heterostructures with a nonmagnetic layer hosting strong spin-orbit coupling (SOC)-remain poorly understood despite nearly three decades since the discovery of ultrafast demagnetization. We introduce a first-principles method to compute these quantities, where the dynamics of charge and current densities is obtained from real-time time-dependent density functional theory, which are then fed into the Jefimenko equations for properly retarded electric and magnetic field solutions of the Maxwell equations. By Fourier transforming different time-dependent terms in the Jefimenko equations, we unravel that in the 0.1-30 THz range the electric field of far-field EM radiation by the Ni layer, chosen as an example, is dominated by charge current pumped by demagnetization, while often invoked magnetic dipole radiation from the time-dependent magnetization of a single magnetic layer is a negligible effect. Such an effect of charge current pumping by a time-dependent quantum system, whose magnetization is shrinking while its vector does not rotate, does not require any spin-to-charge conversion via SOC effects. In the Ni/Pt bilayer, EM radiation remains dominated by the charge current within the Ni layer, whose magnitude is larger than in the case of a single Ni layer due to faster demagnetization, while often invoked spin-to-charge conversion within the Pt layer provides an additional but smaller contribution. By using the Poynting vector and its flux, we also quantify the efficiency of conversion of light into emitted EM radiation, and its angular distribution.
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4
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Liu Y, Xu Y, Fert A, Jaffrès HY, Nie T, Eimer S, Zhang X, Zhao W. Efficient Orbitronic Terahertz Emission Based on CoPt Alloy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2404174. [PMID: 38896111 DOI: 10.1002/adma.202404174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 06/17/2024] [Indexed: 06/21/2024]
Abstract
Orbitronic devices operate by manipulating orbitally polarized currents. Recent studies have shown that these orbital currents can be excited by femtosecond laser pulses in a ferromagnet such as Ni and converted into ultrafast charge currents via orbital-to-charge conversion. However, the terahertz emission from orbitronic terahertz emitters based on Ni is still much weaker than that of the typical spintronic terahertz emitter. Here, this work reports a more efficient light-induced generation of orbital current from a CoPt alloy, and the terahertz emission from CoPt/Cu/MgO is comparable to that of benchmark spintronic terahertz emitters. By varying the composition of the CoPt alloy, the thickness of Cu, and the capping layer, this work confirms that THz emission primarily originates from the orbital accumulation generated within CoPt, propagating through Cu, followed by subsequent orbital-to-charge conversion due to the inverse orbital Rashba-Edelstein effect at the Cu/MgO interface. This study provides strong evidence for the efficient orbital current generation in CoPt alloy, paving the way for efficient orbital terahertz emitters.
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Affiliation(s)
- Yongshan Liu
- National Key Laboratory of Spintronics, Hangzhou International Innovation Institute, Beihang University, Hangzhou, 311115, China
- Fert Beijing Institute, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
| | - Yong Xu
- National Key Laboratory of Spintronics, Hangzhou International Innovation Institute, Beihang University, Hangzhou, 311115, China
- Fert Beijing Institute, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Albert Fert
- Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay, Palaiseau, 91767, France
| | - Henri-Yves Jaffrès
- Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay, Palaiseau, 91767, France
| | - Tianxiao Nie
- Fert Beijing Institute, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Sylvain Eimer
- National Key Laboratory of Spintronics, Hangzhou International Innovation Institute, Beihang University, Hangzhou, 311115, China
| | - Xiaoqiang Zhang
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
| | - Weisheng Zhao
- National Key Laboratory of Spintronics, Hangzhou International Innovation Institute, Beihang University, Hangzhou, 311115, China
- Fert Beijing Institute, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
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5
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Kovalev S, Ilyakov I, Reinold A, Pilch P, Zhu C, Ghalgaoui A, Salikhov R, Lindner J, Wang Z. Terahertz magneto-optical sampling in quartz glass. OPTICS LETTERS 2024; 49:4749-4752. [PMID: 39146151 DOI: 10.1364/ol.534475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2024] [Accepted: 08/01/2024] [Indexed: 08/17/2024]
Abstract
In this Letter, we demonstrate terahertz (THz) magnetic field detection in fused silica with sensitivity that can be easily controlled by sample tilting (for both amplitude and polarization). The proposed technique remains in the linear regime at magnetic fields exceeding 0.3 T (0.9 MV/cm of equivalent electric field) and allows the use of low-cost amorphous materials. Furthermore, the demonstrated effects should be present in a wide variety of materials used as substrates in different THz-pump laser-probe experiments and need to be considered in order to disentangle different contributions to the measured signals.
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Xu X, Zhang D, Liao Z, Yan P, Wang Y, Zhang L, Zhong Z, Bai F, Qu Y, Zhang H, Jin L. Colossal Orbital Current Induced by Gradient Oxidation for High-Efficiency Magnetization Switching. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2403881. [PMID: 39004854 DOI: 10.1002/smll.202403881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2024] [Revised: 06/19/2024] [Indexed: 07/16/2024]
Abstract
Orbital angular momentum flow can be used to develop a low-dissipation electronic information device by manipulating the orbital current. However, efficiently generating and fully harnessing orbital currents is a formidable challenge. In this study, an approach is presented that induces a colossal orbital current by gradient oxidation in Pt/Ta to enhance spin-orbit torque (SOT) and achieve high-efficiency magnetization switching. The maximum efficiency of the SOT before and after the gradient oxidation of Ta is improved relative to that of Pt by ≈600 and 1200%, respectively. The large SOT originates from the colossal orbital current because of the orbital Rashba-Edelstein effect induced by the gradient oxidation of Ta. In addition, a large spin-to-charge conversion efficiency is observed in yttrium iron garnet/Pt/TaOx because of the inverse orbital Rashba-Edelstein effect. Harnessing the orbital current can help effectively minimize the critical current density of the current-induced magnetization switching to 2.26-1.08 × 106 A cm-2, marking a 12-fold reduction compared to that using Pt. This findings provide a new path for research on low-dissipation spin-orbit devices and improve the tunability of orbital current generation.
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Affiliation(s)
- Xinkai Xu
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
| | - Dainan Zhang
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
| | - Zhimin Liao
- State key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing, 100871, P. R. China
| | - Peng Yan
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
| | - Yixin Wang
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
| | - Lei Zhang
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
| | - Zhiyong Zhong
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
| | - Feiming Bai
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
| | - Yuanjing Qu
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
| | - Huaiwu Zhang
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
| | - Lichuan Jin
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China
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Ishii Y, Yamasaki Y, Kozuka Y, Lustikova J, Nii Y, Onose Y, Yokoyama Y, Mizumaki M, Adachi JI, Nakao H, Arima TH, Wakabayashi Y. Microscopic evaluation of spin and orbital moment in ferromagnetic resonance. Sci Rep 2024; 14:15504. [PMID: 38969719 PMCID: PMC11226459 DOI: 10.1038/s41598-024-66139-1] [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: 05/23/2024] [Accepted: 06/27/2024] [Indexed: 07/07/2024] Open
Abstract
Time-resolved X-ray magnetic circular dichroism under the effects of ferromagnetic resonance (FMR), known as X-ray ferromagnetic resonance (XFMR) measurements, enables direct detection of precession dynamics of magnetic moment. Here we demonstrated XFMR measurements and Bayesian analyses as a quantitative probe for the precession of spin and orbital magnetic moments under the FMR effect. Magnetization precessions in two different Pt/Ni-Fe thin film samples were directly detected. Furthermore, the ratio of dynamical spin and orbital magnetic moments was evaluated quantitatively by Bayesian analyses for XFMR energy spectra around the Ni L 2 , 3 absorption edges. Our study paves the way for a microscopic investigation of the contribution of the orbital magnetic moment to magnetization dynamics.
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Affiliation(s)
- Yuta Ishii
- Department of Physics, Tohoku University, Sendai, 980-8578, Japan.
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Japan.
| | - Yuichi Yamasaki
- National Institute for Materials Science (NIMS), Tsukuba, 305-0047, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Yusuke Kozuka
- National Institute for Materials Science (NIMS), Tsukuba, 305-0047, Japan
| | - Jana Lustikova
- Center for Science and Innovation in Spintronics, Tohoku University, Sendai, 980-8577, Japan
| | - Yoichi Nii
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Yoshinori Onose
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Yuichi Yokoyama
- Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), Sayo, 679-5198, Japan
| | - Masaichiro Mizumaki
- Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), Sayo, 679-5198, Japan
- Faculty of Science, Course for Physical Sciences, Kumamoto University, Kumamoto, 860-0862, Japan
| | - Jun-Ichi Adachi
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, 305-0801, Japan
| | - Hironori Nakao
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, 305-0801, Japan
| | - Taka-Hisa Arima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
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8
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Sohn J, Lee JM, Lee HW. Dyakonov-Perel-like Orbital and Spin Relaxations in Centrosymmetric Systems. PHYSICAL REVIEW LETTERS 2024; 132:246301. [PMID: 38949365 DOI: 10.1103/physrevlett.132.246301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Accepted: 05/15/2024] [Indexed: 07/02/2024]
Abstract
The Dyakonov-Perel (DP) mechanism of spin relaxation has long been considered irrelevant in centrosymmetric systems since it was developed originally for noncentrosymmetric ones. We investigate whether this conventional understanding extends to the realm of orbital relaxation, which has recently attracted significant attention. Surprisingly, we find that orbital relaxation in centrosymmetric systems exhibits the DP-like behavior in the weak scattering regime. Moreover, the DP-like orbital relaxation can make the spin relaxation in centrosymmetric systems DP-like through the spin-orbit coupling. We also find that the DP-like orbital and spin relaxations are anisotropic even in materials with high crystal symmetry (such as face-centered cubic structure) and may depend on the orbital and spin nature of electron wave functions.
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9
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Moriya H, Taniguchi M, Jo D, Go D, Soya N, Hayashi H, Mokrousov Y, Lee HW, Ando K. Observation of Long-Range Current-Induced Torque in Ni/Pt Bilayers. NANO LETTERS 2024; 24:6459-6464. [PMID: 38780051 DOI: 10.1021/acs.nanolett.3c05102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
The generation of current-induced torques through the spin Hall effect in Pt has been key to the development of spintronics. In prototypical ferromagnetic-metal/Pt devices, the characteristic length of the torque generation is known to be about 1 nm due to the short spin diffusion length of Pt. Here, we report the observation of a long-range current-induced torque in Ni/Pt bilayers. We demonstrate that when Ni is used as the ferromagnetic layer, the torque efficiency increases with the Pt thickness, even when it exceeds 10 nm. The torque efficiency is also enhanced by increasing the Ni thickness, providing evidence that the observed torque cannot be attributed to the spin Hall effect in the Pt layer. These findings, coupled with our semirealistic tight-binding calculations of the current-induced torque, suggest the possibility that the observed long-range torque is dominated by the orbital Hall effect in the Pt layer.
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Affiliation(s)
- Hiroyuki Moriya
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama 223-8522, Japan
| | - Mari Taniguchi
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama 223-8522, Japan
| | - Daegeun Jo
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Dongwook Go
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
- Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
| | - Nozomi Soya
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama 223-8522, Japan
| | - Hiroki Hayashi
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama 223-8522, Japan
- Keio Institute of Pure and Applied Sciences, Keio University, Yokohama 223-8522, Japan
| | - Yuriy Mokrousov
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
- Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
| | - Hyun-Woo Lee
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Kazuya Ando
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama 223-8522, Japan
- Keio Institute of Pure and Applied Sciences, Keio University, Yokohama 223-8522, Japan
- Center for Spintronics Research Network, Keio University, Yokohama 223-8522, Japan
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Mishra SS, Lourembam J, Lin DJX, Singh R. Active ballistic orbital transport in Ni/Pt heterostructure. Nat Commun 2024; 15:4568. [PMID: 38811558 PMCID: PMC11137139 DOI: 10.1038/s41467-024-48891-0] [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: 01/09/2024] [Accepted: 05/15/2024] [Indexed: 05/31/2024] Open
Abstract
Orbital current, defined as the orbital character of Bloch states in solids, can travel with larger coherence length through a broader range of materials than its spin counterpart, facilitating a robust, higher density and energy efficient information transmission. Hence, active control of orbital transport plays a pivotal role in the progress of the evolving field of quantum information technology. Unlike spin angular momentum, orbital angular momentum couples to phonon angular momentum efficiently via orbital-crystal momentum (L-k) coupling, allowing us to control orbital transport through crystal field potential mediated angular momentum transfer. Here, leveraging the orbital dependant efficient L-k coupling, we have experimentally demonstrated the active control of orbital current velocity in Ni/Pt heterostructure. We observe terahertz emission from Ni/Pt heterostructure via long-range ballistic orbital transport, as evidenced by the delay, and chirping in the emitted THz pulse correlating with increased Pt thickness. Additionally, we also have identified a critical energy density required to overcome collisions in orbital transport, enabling a swifter flow of orbital current. Femtosecond light driven active control of the ballistic orbital transport lays the foundation for the development of dynamic optorbitronics for transmitting information over extended distance.
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Affiliation(s)
- Sobhan Subhra Mishra
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
- Centre for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University, Singapore, 639798, Singapore
| | - James Lourembam
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore, 138364, Singapore
| | - Dennis Jing Xiong Lin
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore, 138364, Singapore
| | - Ranjan Singh
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore.
- Centre for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University, Singapore, 639798, Singapore.
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11
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Liu H, Culcer D. Dominance of Extrinsic Scattering Mechanisms in the Orbital Hall Effect: Graphene, Transition Metal Dichalcogenides, and Topological Antiferromagnets. PHYSICAL REVIEW LETTERS 2024; 132:186302. [PMID: 38759195 DOI: 10.1103/physrevlett.132.186302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Revised: 03/06/2024] [Accepted: 04/02/2024] [Indexed: 05/19/2024]
Abstract
The theory of the orbital Hall effect (OHE), a transverse flow of orbital angular momentum (OAM) in response to an electric field, has concentrated on intrinsic mechanisms. Here, using a quantum kinetic formulation, we determine the full OHE in the presence of short-range disorder using 2D massive Dirac fermions as a prototype. We find that, in doped systems, extrinsic effects associated with the Fermi surface (skew scattering and side jump) provide ≈95% of the OHE. This suggests that, at experimentally relevant transport densities, the OHE is primarily extrinsic.
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Affiliation(s)
- Hong Liu
- School of Physics and Australian Research Council Centre of Excellence in Low-Energy Electronics Technologies, UNSW Node, The University of New South Wales, Sydney 2052, Australia
| | - Dimitrie Culcer
- School of Physics and Australian Research Council Centre of Excellence in Low-Energy Electronics Technologies, UNSW Node, The University of New South Wales, Sydney 2052, Australia
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12
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Xu Y, Zhang F, Fert A, Jaffres HY, Liu Y, Xu R, Jiang Y, Cheng H, Zhao W. Orbitronics: light-induced orbital currents in Ni studied by terahertz emission experiments. Nat Commun 2024; 15:2043. [PMID: 38448561 PMCID: PMC10917802 DOI: 10.1038/s41467-024-46405-6] [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: 02/26/2024] [Indexed: 03/08/2024] Open
Abstract
Orbitronics is based on the use of orbital currents as information carriers. Orbital currents can be generated from the conversion of charge or spin currents, and inversely, they could be converted back to charge or spin currents. Here we demonstrate that orbital currents can also be generated by femtosecond light pulses on Ni. In multilayers associating Ni with oxides and nonmagnetic metals such as Cu, we detect the orbital currents by their conversion into charge currents and the resulting terahertz emission. We show that the orbital currents extraordinarily predominate the light-induced spin currents in Ni-based systems, whereas only spin currents can be detected with CoFeB-based systems. In addition, the analysis of the time delays of the terahertz pulses leads to relevant information on the velocity and propagation length of orbital carriers. Our finding of light-induced orbital currents and our observation of their conversion into charge currents opens new avenues in orbitronics, including the development of orbitronic terahertz devices.
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Affiliation(s)
- Yong Xu
- National Key Lab of Spintronics, International Innovation Institute, Beihang University, Hangzhou, 311115, China
- Fert Beijing Institute, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
| | - Fan Zhang
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
| | - Albert Fert
- Fert Beijing Institute, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China.
- Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay, Palaiseau, 91767, France.
| | - Henri-Yves Jaffres
- Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay, Palaiseau, 91767, France
| | - Yongshan Liu
- Fert Beijing Institute, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
| | - Renyou Xu
- Fert Beijing Institute, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
| | - Yuhao Jiang
- Fert Beijing Institute, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Houyi Cheng
- Fert Beijing Institute, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
| | - Weisheng Zhao
- National Key Lab of Spintronics, International Innovation Institute, Beihang University, Hangzhou, 311115, China.
- Fert Beijing Institute, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China.
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China.
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13
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Adamantopoulos T, Merte M, Go D, Freimuth F, Blügel S, Mokrousov Y. Orbital Rashba Effect as a Platform for Robust Orbital Photocurrents. PHYSICAL REVIEW LETTERS 2024; 132:076901. [PMID: 38427860 DOI: 10.1103/physrevlett.132.076901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 07/03/2023] [Accepted: 01/09/2024] [Indexed: 03/03/2024]
Abstract
Orbital current has emerged over the past years as one of the key novel concepts in magnetotransport. Here, we demonstrate that laser pulses can be used to generate large and robust nonrelativistic orbital currents in systems where the inversion symmetry is broken by the orbital Rashba effect. By referring to model and first principles tools, we demonstrate that orbital Rashba effect, accompanied by crystal field splitting, can mediate robust orbital photocurrents without a need for spin-orbit interaction even in metallic systems. We show that such nonrelativistic orbital photocurrents are translated into derivative photocurrents of spin when relativistic effects are taken into account. We thus promote orbital photocurrents as a promising platform for optical generation of currents of angular momentum, and discuss their possible applications.
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Affiliation(s)
- T Adamantopoulos
- Peter Grünberg Institut, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
- Department of Physics, RWTH Aachen University, 52056 Aachen, Germany
| | - M Merte
- Peter Grünberg Institut, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
- Department of Physics, RWTH Aachen University, 52056 Aachen, Germany
- Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
| | - D Go
- Peter Grünberg Institut, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
- Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
| | - F Freimuth
- Peter Grünberg Institut, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
- Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
| | - S Blügel
- Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
| | - Y Mokrousov
- Peter Grünberg Institut, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
- Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
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14
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Liang H, Ma Y, Yi H, Yao J. Emerging Schemes for Advancing 2D Material Photoconductive-Type Photodetectors. MATERIALS (BASEL, SWITZERLAND) 2023; 16:7372. [PMID: 38068116 PMCID: PMC10707280 DOI: 10.3390/ma16237372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 11/21/2023] [Accepted: 11/25/2023] [Indexed: 10/16/2024]
Abstract
By virtue of the widely tunable band structure, dangling-bond-free surface, gate electrostatic controllability, excellent flexibility, and high light transmittance, 2D layered materials have shown indisputable application prospects in the field of optoelectronic sensing. However, 2D materials commonly suffer from weak light absorption, limited carrier lifetime, and pronounced interfacial effects, which have led to the necessity for further improvement in the performance of 2D material photodetectors to make them fully competent for the numerous requirements of practical applications. In recent years, researchers have explored multifarious improvement methods for 2D material photodetectors from a variety of perspectives. To promote the further development and innovation of 2D material photodetectors, this review epitomizes the latest research progress in improving the performance of 2D material photodetectors, including improvement in crystalline quality, band engineering, interface passivation, light harvesting enhancement, channel depletion, channel shrinkage, and selective carrier trapping, with the focus on their underlying working mechanisms. In the end, the ongoing challenges in this burgeoning field are underscored, and potential strategies addressing them have been proposed. On the whole, this review sheds light on improving the performance of 2D material photodetectors in the upcoming future.
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Affiliation(s)
| | | | | | - Jiandong Yao
- State Key Laboratory of Optoelectronic Materials and Technologies, Nanotechnology Research Center, School of Materials Science & Engineering, Sun Yat-sen University, Guangzhou 510275, China; (H.L.); (Y.M.); (H.Y.)
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15
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Jungfleisch MB. Observation of ultrafast ballistic orbital transport. NATURE NANOTECHNOLOGY 2023; 18:1124-1125. [PMID: 37550572 DOI: 10.1038/s41565-023-01458-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/09/2023]
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