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Gao H, Kong ZZ, Zhang P, Luo Y, Su H, Liu XF, Wang GL, Wang JY, Xu HQ. Gate-defined quantum point contacts in a germanium quantum well. NANOSCALE 2024; 16:10333-10339. [PMID: 38738596 DOI: 10.1039/d4nr00712c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Abstract
We report an experimental study of quantum point contacts defined in a high-quality strained germanium quantum well with layered electric gates. At a zero magnetic field, we observed quantized conductance plateaus in units of 2e2/h. Bias-spectroscopy measurements reveal that the energy spacing between successive one-dimensional subbands ranges from 1.5 to 5 meV as a consequence of the small effective mass of the holes and the narrow gate constrictions. At finite magnetic fields perpendicular to the device plane, the edges of the conductance plateaus get split due to the Zeeman effect and Landé g factors were estimated to be ∼6.6 for the holes in the germanium quantum well. We demonstrate that all quantum point contacts in the same device have comparable performances, indicating a reliable and reproducible device fabrication process. Thus, our work lays a foundation for investigating multiple forefronts of physics in germanium-based quantum devices that require quantum point contacts as building blocks.
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Affiliation(s)
- Han Gao
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and School of Electronics, Peking University, Beijing 100871, China.
| | - Zhen-Zhen Kong
- Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China.
| | - Po Zhang
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China.
| | - Yi Luo
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and School of Electronics, Peking University, Beijing 100871, China.
- Institute of Condensed Matter and Material Physics, School of Physics, Peking University, Beijing 100871, China
| | - Haitian Su
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and School of Electronics, Peking University, Beijing 100871, China.
- Institute of Condensed Matter and Material Physics, School of Physics, Peking University, Beijing 100871, China
| | - Xiao-Fei Liu
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China.
| | - Gui-Lei Wang
- Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China.
- Hefei National Laboratory, University of Science and Technology of China, Hefei, Anhui 230088, China
- Beijing Superstring Academy of Memory Technology, Beijing 100176, China
| | - Ji-Yin Wang
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China.
| | - H Q Xu
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices, and School of Electronics, Peking University, Beijing 100871, China.
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China.
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2
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Xue X, Huang F, Hu G. Spin polarization in quantum point contact based on wurtzite topological quantum well. Phys Chem Chem Phys 2023; 25:26164-26171. [PMID: 37740355 DOI: 10.1039/d3cp02747c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/24/2023]
Abstract
Manipulating spin polarization in wide-gap wurtzite semiconductors is crucial for the development of high-temperature spintronics applications. A topological insulator revealed recently in wurtzite quantum wells (QWs) provides a platform to mediate spin-polarized transport through the polarization field-driven topological edges and large Rashba spin-orbit coupling (SOC). Here, we propose a spin-polarized device in a quantum point contact (QPC) structure based on ZnO/CdO wurtzite topological QWs. The results show that the QPC width can sufficiently control the lateral spin-orbit coupling (SOC) as well as the band gap of the edge states through the quantum size effect. As a result, the spin-polarized conductance exhibits oscillation due to the spin precession, which can be controlled by adjusting the voltage imposed on the split gate. The QPC-induced large spin splitting is highly nonlinear and becomes strong close to the gap. The spin splitting of the edge states will be suppressed for QPC widths greater than 50 nm, and thus lead to an extremely long spin precession length. This QPC width-dependent lateral SOC effect provides an emerging electrical approach to manipulate spin-polarized electron transport in topological wurtzite systems.
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Affiliation(s)
- Xin Xue
- Department of Physics, Lvliang University, Lvliang 03300, China
| | - Fobao Huang
- School of Microelectronics, Northwestern Polytechnical University, Xi'an 710072, China
- Institute of Flexible Electronics, Northwestern Polytechnical University, Xi'an 710072, China
| | - Gongwei Hu
- Hubei Engineering Research Center of Weak Magnetic-field Detection, College of Science, China Three Gorges University, Yichang, 443002, China.
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3
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Chen CH, Lai YT, Chen CF, Wu PT, Su KJ, Hsu SY, Dai GJ, Huang ZY, Hsu CL, Lee SY, Shen CH, Chen HY, Lee CC, Hsieh DR, Lin YF, Chao TS, Lo ST. Single-Gate In-Transistor Readout of Current Superposition and Collapse Utilizing Quantum Tunneling and Ferroelectric Switching. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2301206. [PMID: 37282350 DOI: 10.1002/adma.202301206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 06/01/2023] [Indexed: 06/08/2023]
Abstract
In nanostructure assemblies, the superposition of current paths forms microscopic electric circuits, and different circuit networks produce varying results, particularly when utilized as transistor channels for computing applications. However, the intricate nature of assembly networks and the winding paths of commensurate currents hinder standard circuit modeling. Inspired by the quantum collapse of superposition states for information decoding in quantum circuits, the implementation of analogous current path collapse to facilitate the detection of microscopic circuits by modifying their network topology is explored. Here, the superposition and collapse of current paths in gate-all-around polysilicon nanosheet arrays are demonstrated to enrich the computational resources within transistors by engineering the channel length and quantity. Switching the ferroelectric polarization of Hf0.5 Zr0.5 O2 gate dielectric, which drives these transistors out-of-equilibrium, decodes the output polymorphism through circuit topological modifications. Furthermore, a protocol for the single-electron readout of ferroelectric polarization is presented with tailoring the channel coherence. The introduction of lateral path superposition results into intriguing metal-to-insulator transitions due to transient behavior of ferroelectric switching. This ability to adjust the current networks within transistors and their interaction with ferroelectric polarization in polycrystalline nanostructures lays the groundwork for generating diverse current characteristics as potential physical databases for optimization-based computing.
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Affiliation(s)
- Ching-Hung Chen
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Yu-Ting Lai
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Ciao-Fen Chen
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
- Department of Physics, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Pei-Tzu Wu
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Kuan-Jung Su
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Sheng-Yang Hsu
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Guo-Jin Dai
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Zan-Yi Huang
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Chien-Lung Hsu
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Shen-Yang Lee
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Chuan-Hui Shen
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Hsin-Yu Chen
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Chia-Chin Lee
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Dong-Ru Hsieh
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Yen-Fu Lin
- Department of Physics, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Tien-Sheng Chao
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Shun-Tsung Lo
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
- Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
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4
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Lopes V, Chiappe G, Ribeiro LC, Anda EV. Totally Spin-Polarized Currents in an Interferometer with Spin-Orbit Coupling and the Absence of Magnetic Field Effects. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:4082. [PMID: 36432367 PMCID: PMC9696532 DOI: 10.3390/nano12224082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 11/14/2022] [Accepted: 11/16/2022] [Indexed: 06/16/2023]
Abstract
The paper studies the electronic current in a one-dimensional lead under the effect of spin-orbit coupling and its injection into a metallic conductor through two contacts, forming a closed loop. When an external potential is applied, the time reversal symmetry is broken and the wave vector k of the circulating electrons that contribute to the current is spin-dependent. As the wave function phase depends upon the vector k, the closed path in the circuit produces spin-dependent current interference. This creates a physical scenario in which a spin-polarized current emerges, even in the absence of external magnetic fields or magnetic materials. It is possible to find points in the system's parameter space and, depending upon its geometry, the value of the Fermi energy and the spin-orbit intensities, for which the electronic states participating in the current have only one spin, creating a high and totally spin-polarized conductance. For a potential of a few tens of meV, it is possible to obtain a spin-polarized current of the order of μA. The properties of the obtained electronic current qualify the proposed device as a potentially important tool for spintronics applications.
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Affiliation(s)
- Victor Lopes
- Departamento de Física Aplicada, Universidad de Alicante, San Vicente del Raspeig, 03690 Alicante, Spain
| | - Guillermo Chiappe
- Departamento de Física Aplicada, Universidad de Alicante, San Vicente del Raspeig, 03690 Alicante, Spain
| | - Laercio C. Ribeiro
- Centro Federal de Educação Tecnológica Celso Suckow da Fonseca CEFET/RJ, Campus Nova Iguaçu, Nova Iguaçu, Rio de Janeiro 26041-271, Brazil
| | - Enrique V. Anda
- Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro 22451-900, Brazil
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5
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Pogosov AG, Shevyrin AA, Pokhabov DA, Zhdanov EY, Kumar S. Suspended semiconductor nanostructures: physics and technology. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:263001. [PMID: 35477698 DOI: 10.1088/1361-648x/ac6308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 03/31/2022] [Indexed: 06/14/2023]
Abstract
The current state of research on quantum and ballistic electron transport in semiconductor nanostructures with a two-dimensional electron gas separated from the substrate and nanoelectromechanical systems is reviewed. These nanostructures fabricated using the surface nanomachining technique have certain unexpected features in comparison to their non-suspended counterparts, such as additional mechanical degrees of freedom, enhanced electron-electron interaction and weak heat sink. Moreover, their mechanical functionality can be used as an additional tool for studying the electron transport, complementary to the ordinary electrical measurements. The article includes a comprehensive review of spin-dependent electron transport and multichannel effects in suspended quantum point contacts, ballistic and adiabatic transport in suspended nanostructures, as well as investigations on nanoelectromechanical systems. We aim to provide an overview of the state-of-the-art in suspended semiconductor nanostructures and their applications in nanoelectronics, spintronics and emerging quantum technologies.
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Affiliation(s)
- A G Pogosov
- Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentiev Ave., Novosibirsk 630090, Russia
- Department of Physics, Novosibirsk State University, 2 Pirogov Str., Novosibirsk 630090, Russia
| | - A A Shevyrin
- Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentiev Ave., Novosibirsk 630090, Russia
| | - D A Pokhabov
- Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentiev Ave., Novosibirsk 630090, Russia
- Department of Physics, Novosibirsk State University, 2 Pirogov Str., Novosibirsk 630090, Russia
| | - E Yu Zhdanov
- Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentiev Ave., Novosibirsk 630090, Russia
- Department of Physics, Novosibirsk State University, 2 Pirogov Str., Novosibirsk 630090, Russia
| | - S Kumar
- Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
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6
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Tang P, Iguchi R, Uchida KI, Bauer GEW. Thermoelectric Polarization Transport in Ferroelectric Ballistic Point Contacts. PHYSICAL REVIEW LETTERS 2022; 128:047601. [PMID: 35148138 DOI: 10.1103/physrevlett.128.047601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 11/30/2021] [Indexed: 06/14/2023]
Abstract
We formulate a scattering theory of polarization and heat transport through a ballistic ferroelectric point contact. We predict a polarization current under either an electric field or a temperature difference that depends strongly on the direction of the ferroelectric order and can be detected by its magnetic stray field and associated thermovoltage and Peltier effect.
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Affiliation(s)
- Ping Tang
- WPI-AIMR, Tohoku University, 2-1-1 Katahira, 980-8577 Sendai, Japan
| | - Ryo Iguchi
- National Institute for Materials Science, Tsukuba 305-0047, Japan
| | - Ken-Ichi Uchida
- National Institute for Materials Science, Tsukuba 305-0047, Japan
- Institute for Materials Research, Tohoku University, 2-1-1 Katahira, 980-8577 Sendai, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
| | - Gerrit E W Bauer
- WPI-AIMR, Tohoku University, 2-1-1 Katahira, 980-8577 Sendai, Japan
- Institute for Materials Research, Tohoku University, 2-1-1 Katahira, 980-8577 Sendai, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
- Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, Netherlands
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7
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Smith LW, Chen HB, Chang CW, Wu CW, Lo ST, Chao SH, Farrer I, Beere HE, Griffiths JP, Jones GAC, Ritchie DA, Chen YN, Chen TM. Electrically Controllable Kondo Correlation in Spin-Orbit-Coupled Quantum Point Contacts. PHYSICAL REVIEW LETTERS 2022; 128:027701. [PMID: 35089765 DOI: 10.1103/physrevlett.128.027701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 12/02/2021] [Indexed: 06/14/2023]
Abstract
Integrating the Kondo correlation and spin-orbit interactions, each of which have individually offered unprecedented means to manipulate electron spins, in a controllable way can open up new possibilities for spintronics. We demonstrate electrical control of the Kondo correlation by coupling the bound spin to leads with tunable Rashba spin-orbit interactions, realized in semiconductor quantum point contacts. We observe a transition from single to double peak zero-bias anomalies in nonequilibrium transport-the manifestation of the Kondo effect-indicating a controlled Kondo spin reversal using only spin-orbit interactions. Universal scaling of the Kondo conductance is demonstrated, implying that the spin-orbit interactions could enhance the Kondo temperature. A theoretical model based on quantum master equations is also developed to calculate the nonequilibrium quantum transport.
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Affiliation(s)
- Luke W Smith
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Hong-Bin Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Department of Engineering Science, National Cheng Kung University, Tainan 701, Taiwan
- Center for Quantum Frontiers of Research and Technology (QFort), National Cheng Kung University, Tainan 701, Taiwan
| | - Che-Wei Chang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Chien-Wei Wu
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Shun-Tsung Lo
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan
| | - Shih-Hsiang Chao
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - I Farrer
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
- Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - H E Beere
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - J P Griffiths
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - G A C Jones
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - D A Ritchie
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Yueh-Nan Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Center for Quantum Frontiers of Research and Technology (QFort), National Cheng Kung University, Tainan 701, Taiwan
| | - Tse-Ming Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Center for Quantum Frontiers of Research and Technology (QFort), National Cheng Kung University, Tainan 701, Taiwan
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8
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Yakimenko II, Yakimenko IP. Electronic properties of semiconductor quantum wires for shallow symmetric and asymmetric confinements. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:105302. [PMID: 34852329 DOI: 10.1088/1361-648x/ac3f01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Accepted: 12/01/2021] [Indexed: 06/13/2023]
Abstract
Quantum wires (QWs) and quantum point contacts (QPCs) have been realized in GaAs/AlGaAs heterostructures in which a two-dimensional electron gas resides at the interface between GaAs and AlGaAs layered semiconductors. The electron transport in these structures has previously been studied experimentally and theoretically, and a 0.7 conductance anomaly has been discovered. The present paper is motivated by experiments with a QW in shallow symmetric and asymmetric confinements that have shown additional conductance anomalies at zero magnetic field. The proposed device consists of a QPC that is formed by split gates and a top gate between two large electron reservoirs. This paper is focussed on the theoretical study of electron transport through a wide top-gated QPC in a low-density regime and is based on density functional theory. The electron-electron interaction and shallow confinement make the splitting of the conduction channel into two channels possible. Each of them becomes spin-polarized at certain split and top gates voltages and may contribute to conductance giving rise to additional conductance anomalies. For symmetrically loaded split gates two conduction channels contribute equally to conductance. For the case of asymmetrically applied voltage between split gates conductance anomalies may occur between values of 0.25(2e2/h) and 0.7(2e2/h) depending on the increased asymmetry in split gates voltages. This corresponds to different degrees of spin-polarization in the two conduction channels that contribute differently to conductance. In the case of a strong asymmetry in split gates voltages one channel of conduction is pinched off and just the one remaining channel contributes to conductance. We have found that on the perimeter of the anti-dot there are spin-polarized states. These states may also contribute to conductance if the radius of the anti-dot is small enough and tunneling between these states may occur. The spin-polarized states in the QPC with shallow confinement tuned by electric means may be used for the purposes of quantum technology.
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Affiliation(s)
- Irina I Yakimenko
- Department of Physics, Chemistry and Biology, Linköping University, 58183 Linköping, Sweden
| | - Ivan P Yakimenko
- Department of Physics, Chemistry and Biology, Linköping University, 58183 Linköping, Sweden
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9
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Rana B, Mondal AK, Bandyopadhyay S, Barman A. Applications of nanomagnets as dynamical systems: II. NANOTECHNOLOGY 2021; 33:082002. [PMID: 34644699 DOI: 10.1088/1361-6528/ac2f59] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 10/13/2021] [Indexed: 06/13/2023]
Abstract
In Part I of this topical review, we discussed dynamical phenomena in nanomagnets, focusing primarily on magnetization reversal with an eye to digital applications. In this part, we address mostly wave-like phenomena in nanomagnets, with emphasis on spin waves in myriad nanomagnetic systems and methods of controlling magnetization dynamics in nanomagnet arrays which may have analog applications. We conclude with a discussion of some interesting spintronic phenomena that undergird the rich physics exhibited by nanomagnet assemblies.
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Affiliation(s)
- Bivas Rana
- Institute of Spintronics and Quantum Information, Faculty of Physics, Adam Mickiewicz University in Poznań, Uniwersytetu Poznanskiego 2, Poznań 61-614, Poland
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
| | - Amrit Kumar Mondal
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 106, India
| | - Supriyo Bandyopadhyay
- Department of Electrical and Computer Engineering, Virginia Commonwealth University, Richmond, VA, 23284, United States of America
| | - Anjan Barman
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 106, India
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10
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Mikheev E, Rosen IT, Goldhaber-Gordon D. Quantized critical supercurrent in SrTiO 3-based quantum point contacts. SCIENCE ADVANCES 2021; 7:eabi6520. [PMID: 34597141 PMCID: PMC10938545 DOI: 10.1126/sciadv.abi6520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 08/11/2021] [Indexed: 06/13/2023]
Abstract
Superconductivity in SrTiO3 occurs at remarkably low carrier densities and therefore, unlike conventional superconductors, can be controlled by electrostatic gates. Here, we demonstrate nanoscale weak links connecting superconducting leads, all within a single material, SrTiO3. Ionic liquid gating accumulates carriers in the leads, and local electrostatic gates are tuned to open the weak link. These devices behave as superconducting quantum point contacts with a quantized critical supercurrent. This is a milestone toward establishing SrTiO3 as a single-material platform for mesoscopic superconducting transport experiments that also intrinsically contains the necessary ingredients to engineer topological superconductivity.
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Affiliation(s)
- Evgeny Mikheev
- Department of Physics, Stanford University, Stanford, CA 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Ilan T. Rosen
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
- Department of Applied Physics, Stanford University, Stanford, CA 94305, USA
| | - David Goldhaber-Gordon
- Department of Physics, Stanford University, Stanford, CA 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
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11
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Sakanashi K, Krüger P, Watanabe K, Taniguchi T, Kim GH, Ferry DK, Bird JP, Aoki N. Signature of Spin-Resolved Quantum Point Contact in p-Type Trilayer WSe 2 van der Waals Heterostructure. NANO LETTERS 2021; 21:7534-7541. [PMID: 34472869 DOI: 10.1021/acs.nanolett.1c01828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In this study, an electrostatically induced quantum confinement structure, so-called quantum point contact, has been realized in a p-type trilayer tungsten diselenide-based van der Waals heterostructure with modified van der Waals contact method with degenerately doped transition metal dichalcogenide crystals. Clear quantized conductance and pinch-off state through the one-dimensional confinement were observed by dual-gating of split gate electrodes and top gate. Conductance plateaus were observed at a step of e2/h in addition to quarter plateaus such as 0.25 × 2e2/h at a finite bias voltage condition indicating the signature of intrinsic spin-polarized quantum point contact.
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Affiliation(s)
- Kohei Sakanashi
- Department of Materials Science, Chiba University, Chiba 263-8522, Japan
| | - Peter Krüger
- Department of Materials Science, Chiba University, Chiba 263-8522, Japan
| | - Kenji Watanabe
- International Center for Materials Nanoartchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba 305-0044, Japan
| | - Gil-Ho Kim
- School of Electronic and Electrical Engineering and Sungkyunkwan Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 16419, South Korea
| | - David K Ferry
- School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287, United States
| | - Jonathan P Bird
- Department of Materials Science, Chiba University, Chiba 263-8522, Japan
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Nobuyuki Aoki
- Department of Materials Science, Chiba University, Chiba 263-8522, Japan
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12
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Phong TC, Lam VT, Hoi BD. Tuning electronic phase in noncentrosymmetric quantum spin Hall insulators through physical stimuli. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:325502. [PMID: 34044386 DOI: 10.1088/1361-648x/ac05e4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Accepted: 05/27/2021] [Indexed: 06/12/2023]
Abstract
In this work, the perturbation-induced phase transitions in noncentrosymmetric quantum spin Hall insulators (QSHIs) are analytically addressed. In particular, the dilute charged impurity, the electric field, and the Zeeman splitting field are considered within the tight-binding Hamiltonian model, Green's function approach, and the Born approximation. Following theC3vsymmetry breaking in the PbBiI compound as a representative QSHI, the band gap becomes larger via the electric field, while the system transits to the semimetallic phase via the dilute charged impurities and Zeeman field, modifying the degenerate states in the electronic density of states. While the coexistence of electric field and impurities demonstrate that the system backs to its initial semiconducting phase, the combined Zeeman field and impurities do not alter the robust semimetallic phase.
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Affiliation(s)
- Tran C Phong
- Center for Theoretical and Computational Physics, University of Education, Hue University, Hue 530000, Viet Nam
| | - Vo T Lam
- Faculty of Natural Sciences Pedagogy, Sai Gon University, 273 An Duong Vuong Str., District 5, Ho Chi Minh City, Vietnam
| | - Bui D Hoi
- Center for Theoretical and Computational Physics, University of Education, Hue University, Hue 530000, Viet Nam
- Department of Physics, University of Education, Hue University, Hue 530000, Vietnam
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13
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Demonstration of electron focusing using electronic lenses in low-dimensional system. Sci Rep 2020; 10:2593. [PMID: 32054961 PMCID: PMC7018971 DOI: 10.1038/s41598-020-59453-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 01/20/2020] [Indexed: 11/08/2022] Open
Abstract
We report an all-electric integrable electron focusing lens in n-type GaAs. It is shown that a pronounced focusing peak takes place when the focal point aligns with an on-chip detector. The intensity and full width half maximum (FWHM) of the focusing peak are associated with the collimation of injected electrons. To demonstrate the reported focusing lens can be a useful tool, we investigate the characteristic of an asymmetrically gate biased quantum point contact with the assistance of a focusing lens. A correlation between the occurrence of conductance anomaly in low conductance regime and increase in FWHM of focusing peak is observed. The correlation is likely due to the electron-electron interaction. The reported electron focusing lens is essential for a more advanced electron optics device.
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14
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Width dependence of the 0.5 × (2e 2/h) conductance plateau in InAs quantum point contacts in presence of lateral spin-orbit coupling. Sci Rep 2019; 9:12172. [PMID: 31434942 PMCID: PMC6704071 DOI: 10.1038/s41598-019-48380-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 07/30/2019] [Indexed: 11/22/2022] Open
Abstract
The evolution of the 0.5Go (Go = 2e2/h) conductance plateau and the accompanying hysteresis loop in a series of asymmetrically biased InAs based quantum point contacts (QPCs) in the presence of lateral spin-orbit coupling (LSOC) is studied using a number of QPCs with varying lithographic channel width but fixed channel length. It is found that the size of the hysteresis loops is larger for QPCs of smaller aspect ratio (QPC channel width/length) and gradually disappears as their aspect ratio increases. The physical mechanisms responsible for a decrease in size of the hysteresis loops for QPCs with increasing aspect ratio are: (1) multimode transport in QPCs with larger channel width leading to spin-flip scattering events due to both remote impurities in the doping layer of the heterostructure and surface roughness and impurity (dangling bond) scattering on the sidewalls of the narrow portion of the QPC, and (2) an increase in carrier density resulting in a screening of the electron-electron interactions in the QPC channel. Both effects lead to a progressive disappearance of the net spin polarization in the QPC channel and an accompanying reduction in the size of the hysteresis loops as the lithographic width of the QPC channel increases.
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15
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Lee JS, Shojaei B, Pendharkar M, McFadden AP, Kim Y, Suominen HJ, Kjaergaard M, Nichele F, Zhang H, Marcus CM, Palmstrøm CJ. Transport Studies of Epi-Al/InAs Two-Dimensional Electron Gas Systems for Required Building-Blocks in Topological Superconductor Networks. NANO LETTERS 2019; 19:3083-3090. [PMID: 30912948 DOI: 10.1021/acs.nanolett.9b00494] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
One-dimensional (1D) electronic transport and induced superconductivity in semiconductor nanostructures are crucial ingredients to realize topological superconductivity. Our approach for topological superconductivity employs a two-dimensional electron gas (2DEG) formed by an InAs quantum well, cleanly interfaced with an epitaxial superconductor (epi-Al). This epi-Al/InAs quantum well heterostructure is advantageous for fabricating large-scale nanostructures consisting of multiple Majorana zero modes. Here, we demonstrate transport studies of building-blocks using a high-quality epi-Al/InAs 2DEG heterostructure, which could be put together to realize various proposed 1D nanowire-based nanostructures and 2DEG-based networks that could host multiple Majorana zero modes. The studies include (1) gate-defined quasi-1D channels in the InAs 2DEG and (2) quantum point contacts for tunneling spectroscopy, as well as induced superconductivity in (3) a ballistic Al-InAs 2DEG-Al Josephson junction. From 1D transport, systematic evolution of conductance plateaus in half-integer conductance quanta is observed with Landé g-factor of 17, indicating the strong spin-orbit coupling and high quality of the InAs 2DEG. The improved 2DEG quality leads to ballistic Josephson junctions with enhanced characteristic parameters such as Ic Rn and Iexc Rn, the product of superconducting critical current Ic (and excess current Iexc) and normal resistance Rn. Our results of electronic transport studies based on the 2D approach suggest that the epitaxial superconductor/2D semiconductor system with improved 2DEG quality is suitable for realizing large-scale nanostructures for quantum computing applications.
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Affiliation(s)
| | | | | | | | | | - Henri J Suominen
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute , University of Copenhagen , Universitetsparken 5 , 2100 Copenhagen , Denmark
| | - Morten Kjaergaard
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute , University of Copenhagen , Universitetsparken 5 , 2100 Copenhagen , Denmark
| | - Fabrizio Nichele
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute , University of Copenhagen , Universitetsparken 5 , 2100 Copenhagen , Denmark
| | - Hao Zhang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics , Tsinghua University , Beijing 100084 , People's Republic of China
| | - Charles M Marcus
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute , University of Copenhagen , Universitetsparken 5 , 2100 Copenhagen , Denmark
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16
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Gul Y, Creeth GL, English D, Holmes SN, Thomas KJ, Farrer I, Ellis DJ, Ritchie DA, Pepper M. Conductance quantisation in patterned gate In 0.75Ga 0.25As structures up to 6 × (2e 2/h). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:104002. [PMID: 30625452 DOI: 10.1088/1361-648x/aafd05] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We present electrical measurements from In0.75Ga0.25As 1D channel devices with Rashba-type, spin-orbit coupling present in the 2D contact regions. Suppressed backscattering as a result of the time-reversal asymmetry at the 1D channel entrance results in enhanced ballistic transport characteristics with clear quantised conductance plateaus up to 6 × (2e 2/h). Applying DC voltages between the source and drain ohmic contacts and an in-plane magnetic field confirms a ballistic transport picture. For asymmetric patterned gate biasing, a lateral spin-orbit coupling effect is weak. However, the Rashba-type spin-orbit coupling leads to a g-factor in the 1D channel that is reduced in magnitude from the 2D value of 9 to ~6.5 in the lowest subband when the effective Rashba field and the applied magnetic field are perpendicular.
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Affiliation(s)
- Y Gul
- London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
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17
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Kohda M, Okayasu T, Nitta J. Spin-momentum locked spin manipulation in a two-dimensional Rashba system. Sci Rep 2019; 9:1909. [PMID: 30760759 PMCID: PMC6374388 DOI: 10.1038/s41598-018-37967-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 12/17/2018] [Indexed: 11/22/2022] Open
Abstract
Spin-momentum locking, which constrains spin orientation perpendicular to electron momentum, is attracting considerable interest for exploring various spin functionalities in semiconductors and topological materials. Efficient spin generation and spin detection have been demonstrated using the induced helical spin texture. Nevertheless, spin manipulation by spin-momentum locking remains a missing piece because, once bias voltage is applied to induce the current flow, the spin orientation must be locked by the electron momentum direction, thereby rendering spin phase control difficult. Herein, we demonstrate the spin-momentum locking-induced spin manipulation for ballistic electrons in a strong Rashba two-dimensional system. Electron spin rotates in a circular orbital motion for ballistically moving electrons, although spin orientation is locked towards the spin-orbit field because of the helical spin texture. This fact demonstrates spin manipulation by control of the electron orbital motion and reveals potential effects of the orbital degree of freedom on the spin phase for future spintronic and topological devices and for the processing of quantum information.
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Affiliation(s)
- Makoto Kohda
- Department of Materials Science, Tohoku University, 6-6-02 Aramaki-Aza Aoba, Aoba-ku, Sendai, 980-8579, Japan. .,Center for Spintronics Research Network, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan. .,Center for Science and Innovation in Spintronics (Core Research Cluster), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.
| | - Takanori Okayasu
- Department of Materials Science, Tohoku University, 6-6-02 Aramaki-Aza Aoba, Aoba-ku, Sendai, 980-8579, Japan
| | - Junsaku Nitta
- Department of Materials Science, Tohoku University, 6-6-02 Aramaki-Aza Aoba, Aoba-ku, Sendai, 980-8579, Japan.,Center for Spintronics Research Network, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.,Center for Science and Innovation in Spintronics (Core Research Cluster), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan
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18
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Chou CT, Jacobson NT, Moussa JE, Baczewski AD, Chuang Y, Liu CY, Li JY, Lu TM. Weak anti-localization of two-dimensional holes in germanium beyond the diffusive regime. NANOSCALE 2018; 10:20559-20564. [PMID: 30256364 DOI: 10.1039/c8nr05677c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Gate-controllable spin-orbit coupling is often one requisite for spintronic devices. For practical spin field-effect transistors, another essential requirement is ballistic spin transport, where the spin precession length is shorter than the mean free path such that the gate-controlled spin precession is not randomized by disorder. In this letter, we report the observation of a gate-induced crossover from weak localization to weak anti-localization in the magneto-resistance of a high-mobility two-dimensional hole gas in a strained germanium quantum well. From the magneto-resistance, we extract the phase-coherence time, spin-orbit precession time, spin-orbit energy splitting, and cubic Rashba coefficient over a wide density range. The mobility and the mean free path increase with increasing hole density, while the spin precession length decreases due to increasingly stronger spin-orbit coupling. As the density becomes larger than ∼6 × 1011 cm-2, the spin precession length becomes shorter than the mean free path, and the system enters the ballistic spin transport regime. We also report here the numerical methods and code developed for calculating the magneto-resistance in the ballistic regime, where the commonly used HLN and ILP models for analyzing weak localization and anti-localization are not valid. These results pave the way toward silicon-compatible spintronic devices.
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Affiliation(s)
- C-T Chou
- Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan.
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19
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Sun J, Deacon RS, Wang R, Yao J, Lieber CM, Ishibashi K. Helical Hole State in Multiple Conduction Modes in Ge/Si Core/Shell Nanowire. NANO LETTERS 2018; 18:6144-6149. [PMID: 30226052 DOI: 10.1021/acs.nanolett.8b01799] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Helical states, a prerequisite for the engineering of Majorana zero modes in solid-state systems, have recently been reported in the conduction band of III-V nanowires (NWs) subject to strong Rashba spin-orbit interaction. We report the observation of re-entrant conductance features consistent with the presence of helical hole states in multiple conduction modes of a Ge/Si core/shell NW. The Ge/Si system has several potential advantages over electron systems such as longer spin coherence time due to weaker coupling to nuclear spins and the possibility of isotope-purified materials for nuclear spin-free devices. We derive the Landé g factor of 3.6 from magneto-transport measurements, comparable to theoretical predictions and significantly larger when compared with that in strongly confined quantum dots. The spin-orbit energy is evaluated as ∼2.1 meV, on par with values in III-V NWs, showing good agreement with previous theoretical predictions and weak antilocalization measurements.
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Affiliation(s)
- Jian Sun
- Advanced Device Laboratory , RIKEN , 2-1 Hirosawa , Wako, Saitama 351-0198 , Japan
- School of Physical Science and Electronics , Central South University , Changsha 410083 , China
| | - Russell S Deacon
- Advanced Device Laboratory , RIKEN , 2-1 Hirosawa , Wako, Saitama 351-0198 , Japan
- Center for Emergent Matter Science , RIKEN , Wako, Saitama 351-0198 , Japan
| | - Rui Wang
- Advanced Device Laboratory , RIKEN , 2-1 Hirosawa , Wako, Saitama 351-0198 , Japan
| | - Jun Yao
- Deparment of Chemistry and Chemical Biology , Harvard University , Cambridge , Massachusetts 02138 , United States
- Department of Electrical and Computer Engineering, Institute for Applied Life Sciences , University of Massachusetts , Amherst , Massachusetts 01003 , United States
| | - Charles M Lieber
- Deparment of Chemistry and Chemical Biology , Harvard University , Cambridge , Massachusetts 02138 , United States
- School of Engineering and Applied Sciences , Harvard University , Cambridge , Massachusetts 02138 , United States
| | - Koji Ishibashi
- Advanced Device Laboratory , RIKEN , 2-1 Hirosawa , Wako, Saitama 351-0198 , Japan
- Center for Emergent Matter Science , RIKEN , Wako, Saitama 351-0198 , Japan
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20
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Karlsson H, Yakimenko II, Berggren KF. Nature of magnetization and lateral spin-orbit interaction in gated semiconductor nanowires. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:215302. [PMID: 29623898 DOI: 10.1088/1361-648x/aabc15] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Semiconductor nanowires are interesting candidates for realization of spintronics devices. In this paper we study electronic states and effects of lateral spin-orbit coupling (LSOC) in a one-dimensional asymmetrically biased nanowire using the Hartree-Fock method with Dirac interaction. We have shown that spin polarization can be triggered by LSOC at finite source-drain bias,as a result of numerical noise representing a random magnetic field due to wiring or a random background magnetic field by Earth magnetic field, for instance. The electrons spontaneously arrange into spin rows in the wire due to electron interactions leading to a finite spin polarization. The direction of polarization is, however, random at zero source-drain bias. We have found that LSOC has an effect on orientation of spin rows only in the case when source-drain bias is applied.
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21
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Kolasiński K, Sellier H, Szafran B. Extraction of the Rashba spin-orbit coupling constant from scanning gate microscopy conductance maps for quantum point contacts. Sci Rep 2017; 7:14935. [PMID: 29097691 PMCID: PMC5668439 DOI: 10.1038/s41598-017-14380-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 10/09/2017] [Indexed: 11/09/2022] Open
Abstract
We study the possibility for the extraction of the Rashba spin-orbit coupling constant for a two-dimensional electron gas with the conductance microscopy technique. Due to the interplay between the effective magnetic field due to the Rashba spin-orbit coupling and the external magnetic field applied within the plane of confinement, the electron backscattering induced by a charged tip of an atomic force microscope located above the sample leads to the spin precession and spin mixing of the incident and reflected electron waves between the QPC and the tip-induced 2DEG depletion region. This mixing leads to a characteristic angle-dependent beating pattern visible in the conductance maps. We show that the structure of the Fermi level, bearing signatures of the spin-orbit coupling, can be extracted from the Fourier transform of the interference fringes in the conductance maps as a function of the magnetic field direction. We propose a simple analytical model which can be used to fit the experimental data in order to obtain the spin-orbit coupling constant.
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Affiliation(s)
- K Kolasiński
- AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059, Kraków, Poland
| | - H Sellier
- Université Grenoble Alpes, CNRS, Institut Néel, 38000, Grenoble, France
| | - B Szafran
- AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059, Kraków, Poland.
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22
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Controlled spatial separation of spins and coherent dynamics in spin-orbit-coupled nanostructures. Nat Commun 2017; 8:15997. [PMID: 28691707 PMCID: PMC5508128 DOI: 10.1038/ncomms15997] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 05/17/2017] [Indexed: 11/08/2022] Open
Abstract
The spatial separation of electron spins followed by the control of their individual spin dynamics has recently emerged as an essential ingredient in many proposals for spin-based technologies because it would enable both of the two spin species to be simultaneously utilized, distinct from most of the current spintronic studies and technologies wherein only one spin species could be handled at a time. Here we demonstrate that the spatial spin splitting of a coherent beam of electrons can be achieved and controlled using the interplay between an external magnetic field and Rashba spin-orbit interaction in semiconductor nanostructures. The technique of transverse magnetic focusing is used to detect this spin separation. More notably, our ability to engineer the spin-orbit interactions enables us to simultaneously manipulate and probe the coherent spin dynamics of both spin species and hence their correlation, which could open a route towards spintronics and spin-based quantum information processing.
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23
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Spin filtering effect generated by the inter-subband spin-orbit coupling in the bilayer nanowire with the quantum point contact. Sci Rep 2017; 7:45346. [PMID: 28358141 PMCID: PMC5371906 DOI: 10.1038/srep45346] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 02/27/2017] [Indexed: 11/23/2022] Open
Abstract
The spin filtering effect in the bilayer nanowire with quantum point contact is investigated theoretically. We demonstrate the new mechanism of the spin filtering based on the lateral inter-subband spin-orbit coupling, which for the bilayer nanowires has been reported to be strong. The proposed spin filtering effect is explained as the joint effect of the Landau-Zener intersubband transitions caused by the hybridization of states with opposite spin (due to the lateral Rashba SO interaction) and the confinement of carriers in the quantum point contact region.
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24
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Yakimenko II, Berggren KF. Probing dopants in wide semiconductor quantum point contacts. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:105801. [PMID: 26885626 DOI: 10.1088/0953-8984/28/10/105801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Effects of randomly distributed impurities on conductance, spin polarization and electron localization in realistic gated semiconductor quantum point contacts (QPCs) have been simulated numerically. To this end density functional theory in the local spin-density approximation has been used. In the case when the donor layer is embedded far from the two-dimensional electron gas (2DEG) the electrostatic confinement potential exhibits the conventional parabolic form, and thus the usual ballistic transport phenomena take place both in the devices with split gates alone and with an additional metallic gate on the top. In the opposite case, i.e. when the randomly distributed donors are placed not far away from the 2DEG layer, there are drastic changes like the localization of electrons in the vicinity of confinement potential minima which give rise to fluctuations in conductance and resonances. The conductance as a function of the voltage applied to the top gate for asymmetrically charged split gates has been calculated. In this case resonances in conductance caused by randomly distributed donors are shifted and decrease in amplitude while the anomalies caused by interaction effects remain unmodified. It has been also shown that for a wide QPC the polarization can appear in the form of stripes. The importance of partial ionization of the random donors and the possibility of short range order among the ionized donors are emphasized. The motivation for this work is to critically evaluate the nature of impurities and how to guide the design of high-mobility devices.
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Affiliation(s)
- I I Yakimenko
- Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping, Sweden
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25
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Farghadan R, Sehat A. Enhancement of Rashba spin–orbit coupling by electron–electron interaction. RSC Adv 2016. [DOI: 10.1039/c6ra16289d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We studied how the electron–electron interaction enhances the strength of the Rashba spin–orbit coupling and opens the possibility of generating a spin-polarized output current from an unpolarized electric current without any magnetic elements.
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Affiliation(s)
| | - Ali Sehat
- Department of Physics
- University of Kashan
- Kashan
- Iran
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26
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Manchon A, Koo HC, Nitta J, Frolov SM, Duine RA. New perspectives for Rashba spin-orbit coupling. NATURE MATERIALS 2015; 14:871-882. [PMID: 26288976 DOI: 10.1038/nmat4360] [Citation(s) in RCA: 420] [Impact Index Per Article: 46.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Accepted: 06/22/2015] [Indexed: 06/04/2023]
Abstract
In 1984, Bychkov and Rashba introduced a simple form of spin-orbit coupling to explain the peculiarities of electron spin resonance in two-dimensional semiconductors. Over the past 30 years, Rashba spin-orbit coupling has inspired a vast number of predictions, discoveries and innovative concepts far beyond semiconductors. The past decade has been particularly creative, with the realizations of manipulating spin orientation by moving electrons in space, controlling electron trajectories using spin as a steering wheel, and the discovery of new topological classes of materials. This progress has reinvigorated the interest of physicists and materials scientists in the development of inversion asymmetric structures, ranging from layered graphene-like materials to cold atoms. This Review discusses relevant recent and ongoing realizations of Rashba physics in condensed matter.
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Affiliation(s)
- A Manchon
- King Abdullah University of Science and Technology (KAUST), Physical Science and Engineering Division, Thuwal 23955-6900, Saudi Arabia
| | - H C Koo
- Center for Spintronics, Korea Institute of Science and Technology (KIST), 39-1 Hawolgok-dong, Seongbukgu, Seoul 136-791, Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 136-701, Korea
| | - J Nitta
- Department of Materials Science, Tohoku University, 980-8579 Sendai, Miyagi, Japan
| | - S M Frolov
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - R A Duine
- Institute for Theoretical Physics and Center for Extreme Matter and Emergent Phenomena, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht, The Netherlands
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27
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Electric-field-induced Spontaneous Magnetization and Phase Transitions in Zigzag Boron Nitride Nanotubes. Sci Rep 2015. [PMID: 26206393 PMCID: PMC4513305 DOI: 10.1038/srep12416] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We demonstrate an alternative scheme for realizing spin polarizations in semiconductor nanostructures by an all-electric way. The electronic and magnetic properties of the model system, zigzag pristine boron nitride nanotubes (BNNTs), are investigated under a transverse electric field (E) through spin-polarized density functional theory calculations. As E increases, the band gap of BNNTs is reduced due to charge redistribution induced by the asymmetry of electrostatic potential energy, and BNNTs experience rich phase transitions, such as semiconductor-metal transition and nonmagnetic (NM) metal-ferromagnetic (FM) metal transitions. Electric-field-induced magnetization occurs when a sufficiently high density of states at the Fermi level in the vicinity of metal-insulator transition is reached due to the redistribution of electronic bands and charge transferring across the BNNTs. Further analysis show that the spontaneous magnetization is derived from the localized nature of the 2p states of B and N, and the ferromagnetic coupling is stabilized by Zener’s double-exchange mechanism. Our results may provide a viable way to realize spintronic devices for applications.
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28
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Chico L, Latgé A, Brey L. Symmetries of quantum transport with Rashba spin–orbit: graphene spintronics. Phys Chem Chem Phys 2015; 17:16469-75. [DOI: 10.1039/c5cp01637a] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The lack of some spatial symmetries in planar devices with Rashba spin–orbit interactions opens up the possibility of producing spin polarized electrical currents in the absence of external magnetic fields or magnetic impurities.
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Affiliation(s)
- Leonor Chico
- Instituto de Ciencia de Materiales de Madrid
- Consejo Superior de Investigaciones Científicas
- 28049 Madrid
- Spain
| | - Andrea Latgé
- Instituto de Física
- Universidade Federal Fluminense
- RJ
- Brazil
| | - Luis Brey
- Instituto de Ciencia de Materiales de Madrid
- Consejo Superior de Investigaciones Científicas
- 28049 Madrid
- Spain
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29
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Chuang P, Ho SC, Smith LW, Sfigakis F, Pepper M, Chen CH, Fan JC, Griffiths JP, Farrer I, Beere HE, Jones GAC, Ritchie DA, Chen TM. All-electric all-semiconductor spin field-effect transistors. NATURE NANOTECHNOLOGY 2015; 10:35-39. [PMID: 25531088 DOI: 10.1038/nnano.2014.296] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 11/11/2014] [Indexed: 06/04/2023]
Abstract
The spin field-effect transistor envisioned by Datta and Das opens a gateway to spin information processing. Although the coherent manipulation of electron spins in semiconductors is now possible, the realization of a functional spin field-effect transistor for information processing has yet to be achieved, owing to several fundamental challenges such as the low spin-injection efficiency due to resistance mismatch, spin relaxation and the spread of spin precession angles. Alternative spin transistor designs have therefore been proposed, but these differ from the field-effect transistor concept and require the use of optical or magnetic elements, which pose difficulties for incorporation into integrated circuits. Here, we present an all-electric and all-semiconductor spin field-effect transistor in which these obstacles are overcome by using two quantum point contacts as spin injectors and detectors. Distinct engineering architectures of spin-orbit coupling are exploited for the quantum point contacts and the central semiconductor channel to achieve complete control of the electron spins (spin injection, manipulation and detection) in a purely electrical manner. Such a device is compatible with large-scale integration and holds promise for future spintronic devices for information processing.
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Affiliation(s)
- Pojen Chuang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Sheng-Chin Ho
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - L W Smith
- Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - F Sfigakis
- Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - M Pepper
- Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, UK
| | - Chin-Hung Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Ju-Chun Fan
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - J P Griffiths
- Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - I Farrer
- Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - H E Beere
- Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - G A C Jones
- Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - D A Ritchie
- Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - Tse-Ming Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
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Cahay M. Spin transistors: Closer to an all-electric device. NATURE NANOTECHNOLOGY 2015; 10:21-22. [PMID: 25531087 DOI: 10.1038/nnano.2014.305] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Affiliation(s)
- Marc Cahay
- Department of Electrical Engineering and Computing Systems, University of Cincinnati, Cincinnati, Ohio 45221, USA
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31
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Abstract
Superconductivity and spin-orbit (SO) interaction have been two separate emerging fields until very recently that the correlation between them seemed to be observed. However, previous experiments concerning SO coupling are performed far beyond the superconducting state and thus a direct demonstration of how SO coupling affects superconductivity remains elusive. Here we investigate the SO coupling in the critical region of superconducting transition on Al nanofilms, in which the strength of disorder and spin relaxation by SO coupling are changed by varying the film thickness. At temperatures T sufficiently above the superconducting critical temperature Tc, clear signature of SO coupling reveals itself in showing a magneto-resistivity peak. When T < Tc, the resistivity peak can still be observed; however, its line-shape is now affected by the onset of the quasi two-dimensional superconductivity. By studying such magneto-resistivity peaks under different strength of spin relaxation, we highlight the important effects of SO interaction on superconductivity.
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Xiang S, Xiao S, Fuji K, Shibuya K, Endo T, Yumoto N, Morimoto T, Aoki N, Bird JP, Ochiai Y. On the zero-bias anomaly and Kondo physics in quantum point contacts near pinch-off. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:125304. [PMID: 24599094 DOI: 10.1088/0953-8984/26/12/125304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We investigate the linear and non-linear conductance of quantum point contacts (QPCs), in the region near pinch-off where Kondo physics has previously been connected to the appearance of the 0.7 feature. In studies of seven different QPCs, fabricated in the same high-mobility GaAs/AlGaAs heterojunction, the linear conductance is widely found to show the presence of the 0.7 feature. The differential conductance, on the other hand, does not generally exhibit the zero-bias anomaly (ZBA) that has been proposed to indicate the Kondo effect. Indeed, even in the small subset of QPCs found to exhibit such an anomaly, the linear conductance does not always follow the universal temperature-dependent scaling behavior expected for the Kondo effect. Taken collectively, our observations demonstrate that, unlike the 0.7 feature, the ZBA is not a generic feature of low-temperature QPC conduction. We furthermore conclude that the mere observation of the ZBA alone is insufficient evidence for concluding that Kondo physics is active. While we do not rule out the possibility that the Kondo effect may occur in QPCs, our results appear to indicate that its observation requires a very strict set of conditions to be satisfied. This should be contrasted with the case of the 0.7 feature, which has been apparent since the earliest experimental investigations of QPC transport.
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Affiliation(s)
- S Xiang
- Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
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Khatua P, Bansal B, Shahar D. Single-slit electron diffraction with Aharonov-Bohm phase: Feynman's thought experiment with quantum point contacts. PHYSICAL REVIEW LETTERS 2014; 112:010403. [PMID: 24483873 DOI: 10.1103/physrevlett.112.010403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2013] [Indexed: 06/03/2023]
Abstract
In a "thought experiment," now a classic in physics pedagogy, Feynman visualizes Young's double-slit interference experiment with electrons in magnetic field. He shows that the addition of an Aharonov-Bohm phase is equivalent to shifting the zero-field wave interference pattern by an angle expected from the Lorentz force calculation for classical particles. We have performed this experiment with one slit, instead of two, where ballistic electrons within two-dimensional electron gas diffract through a small orifice formed by a quantum point contact (QPC). As the QPC width is comparable to the electron wavelength, the observed intensity profile is further modulated by the transverse waveguide modes present at the injector QPC. Our experiments open the way to realizing diffraction-based ideas in mesoscopic physics.
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Affiliation(s)
- Pradip Khatua
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel and Indian Institute of Science Education and Research Kolkata, Mohanpur Campus, Nadia 741252, West Bengal, India
| | - Bhavtosh Bansal
- Indian Institute of Science Education and Research Kolkata, Mohanpur Campus, Nadia 741252, West Bengal, India
| | - Dan Shahar
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel
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34
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Kohda M, Nakamura S, Nishihara Y, Kobayashi K, Ono T, Ohe JI, Tokura Y, Mineno T, Nitta J. Spin-orbit induced electronic spin separation in semiconductor nanostructures. Nat Commun 2013; 3:1082. [PMID: 23011136 PMCID: PMC3658013 DOI: 10.1038/ncomms2080] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 08/22/2012] [Indexed: 11/29/2022] Open
Abstract
The demonstration of quantized spin splitting by Stern and Gerlach is one of the most important experiments in modern physics. Their discovery was the precursor of recent developments in spin-based technologies. Although electrical spin separation of charged particles is fundamental in spintronics, in non-uniform magnetic fields it has been difficult to separate the spin states of charged particles due to the Lorentz force, as well as to the insufficient and uncontrollable field gradients. Here we demonstrate electronic spin separation in a semiconductor nanostructure. To avoid the Lorentz force, which is inevitably induced when an external magnetic field is applied, we utilized the effective non-uniform magnetic field which originates from the Rashba spin–orbit interaction in an InGaAs-based heterostructure. Using a Stern–Gerlach-inspired mechanism, together with a quantum point contact, we obtained field gradients of 108 T m−1 resulting in a highly polarized spin current. Achieving spin separation of charged particles in non-uniform magnetic fields is hindered by the Lorentz force. Kohda et al. demonstrate spin separation in a semiconductor nanostructure by exploiting the effective magnetic field arising from the spin–orbit interaction and achieve highly polarized spin currents.
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Affiliation(s)
- Makoto Kohda
- Department of Materials Science, Tohoku University, 6-6-02 Aramaki-Aza Aoba, Aoba-ku, Sendai 980-8579, Japan.
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35
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Chen TM, Pepper M, Farrer I, Jones GAC, Ritchie DA. All-electrical injection and detection of a spin-polarized current using 1D conductors. PHYSICAL REVIEW LETTERS 2012; 109:177202. [PMID: 23215217 DOI: 10.1103/physrevlett.109.177202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Revised: 09/06/2012] [Indexed: 06/01/2023]
Abstract
All-electrical control of spin transport in nanostructures has been the central interest and challenge of spin physics and spintronics. Here we demonstrate on-chip spin polarizing or filtering actions by driving the gate-defined one dimensional (1D) conductor, one of the simplest geometries for integrated quantum devices, away from the conventional Ohmic regime. Direct measurement of the spin polarization of the emitted current was performed when the momentum degeneracy was lifted, wherein both the 1D polarizer for spin injection and the analyzer for spin detection were demonstrated. The results showed that a configuration of gates and applied voltages can give rise to a tunable spin polarization, which has implications for the development of spintronic devices and future quantum information processing.
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Affiliation(s)
- T-M Chen
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan.
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36
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Li X, Wu X, Li Z, Yang J, Hou JG. Bipolar magnetic semiconductors: a new class of spintronics materials. NANOSCALE 2012; 4:5680-5685. [PMID: 22874973 DOI: 10.1039/c2nr31743e] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Electrical control of spin polarization is very desirable in spintronics, since electric fields can be easily applied locally, in contrast to magnetic fields. Here, we propose a new concept of bipolar magnetic semiconductors (BMS) in which completely spin-polarized currents with reversible spin polarization can be created and controlled simply by applying a gate voltage. This is a result of the unique electronic structure of BMS, where the valence and conduction bands possess opposite spin polarization when approaching the Fermi level. BMS is thus expected to have potential for various applications. Our band structure and spin-polarized electronic transport calculations on semi-hydrogenated single-walled carbon nanotubes confirm the existence of BMS materials and demonstrate the electrical control of spin-polarization in them.
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Affiliation(s)
- Xingxing Li
- Hefei National Laboratory of Physical Science at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
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37
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Burke AM, Klochan O, Farrer I, Ritchie DA, Hamilton AR, Micolich AP. Extreme sensitivity of the spin-splitting and 0.7 anomaly to confining potential in one-dimensional nanoelectronic devices. NANO LETTERS 2012; 12:4495-4502. [PMID: 22830617 DOI: 10.1021/nl301566d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Quantum point contacts (QPCs) have shown promise as nanoscale spin-selective components for spintronic applications and are of fundamental interest in the study of electron many-body effects such as the 0.7 × 2e(2)/h anomaly. We report on the dependence of the 1D Landé g-factor g and 0.7 anomaly on electron density and confinement in QPCs with two different top-gate architectures. We obtain g values up to 2.8 for the lowest 1D subband, significantly exceeding previous in-plane g-factor values in AlGaAs/GaAs QPCs and approaching that in InGaAs/InP QPCs. We show that g is highly sensitive to confinement potential, particularly for the lowest 1D subband. This suggests careful management of the QPC's confinement potential may enable the high g desirable for spintronic applications without resorting to narrow-gap materials such as InAs or InSb. The 0.7 anomaly and zero-bias peak are also highly sensitive to confining potential, explaining the conflicting density dependencies of the 0.7 anomaly in the literature.
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Affiliation(s)
- A M Burke
- School of Physics, University of New South Wales, Sydney NSW 2052, Australia.
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38
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Das PP, Bhandari NK, Wan J, Charles J, Cahay M, Chetry KB, Newrock RS, Herbert ST. Influence of surface scattering on the anomalous conductance plateaus in an asymmetrically biased InAs/In(0.52)Al(0.48)As quantum point contact. NANOTECHNOLOGY 2012; 23:215201. [PMID: 22551945 DOI: 10.1088/0957-4484/23/21/215201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We study of the appearance and evolution of several anomalous (i.e., G < G(0) D 2e(2)/h) conductance plateaus in an In(0.52)Al(0.48)As/InAs quantum point contact (QPC). This work was performed at T = 4:2 K as a function of the offset bias ΔV(G) between the two in-plane gates of the QPC. The number and location of the anomalous conductance plateaus strongly depend on the polarity of the offset bias. The anomalous plateaus appear only over an intermediate range of offset bias of several volts. They are quite robust, being observed over a maximum range of nearly 1 V for the common sweep voltage applied to the two gates. These results are interpreted as evidence for the sensitivity of the QPC spin polarization to defects (surface roughness and impurity (dangling bond) scattering) generated during the etching process that forms the QPC side walls. This assertion is supported by non-equilibrium Green function simulations of the conductance of a single QPC in the presence of dangling bonds on its walls. Our simulations show that a spin conductance polarization as high as 98% can be achieved despite the presence of dangling bonds. The maximum in is not necessarily reached where the conductance of the channel is equal to 0:5G(0).
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Affiliation(s)
- Partha P Das
- School of Electronics and Computing Systems, University of Cincinnati, Cincinnati, OH 45221, USA
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Micolich AP. What lurks below the last plateau: experimental studies of the 0.7 × 2e(2)/h conductance anomaly in one-dimensional systems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:443201. [PMID: 21997403 DOI: 10.1088/0953-8984/23/44/443201] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The integer quantised conductance of one-dimensional electron systems is a well-understood effect of quantum confinement. A number of fractionally quantised plateaus are also commonly observed. They are attributed to many-body effects, but their precise origin is still a matter of debate, having attracted considerable interest over the past 15 years. This review reports on experimental studies of fractionally quantised plateaus in semiconductor quantum point contacts and quantum wires, focusing on the 0.7 × 2e(2)/h conductance anomaly, its analogues at higher conductances and the zero-bias peak observed in the dc source-drain bias for conductances less than 2e(2)/h.
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Affiliation(s)
- A P Micolich
- School of Physics, University of New South Wales, Sydney, NSW 2052, Australia.
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40
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Fransson J, Galperin M. Spin seebeck coefficient of a molecular spin pump. Phys Chem Chem Phys 2011; 13:14350-7. [DOI: 10.1039/c1cp20720b] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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41
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Liu KM, Juang CH, Umansky V, Hsu SY. Effect of impurity scattering on the linear and nonlinear conductances of quasi-one-dimensional disordered quantum wires by asymmetrically lateral confinement. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:395303. [PMID: 21403225 DOI: 10.1088/0953-8984/22/39/395303] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We have studied the linear conductance and source-drain bias spectroscopies of clean and disordered quantum wires (QWs) against thermal cycling and lateral shifting, which change the impurity configuration. Conductance quantization and the zero bias anomaly (ZBA) are robust in clean QWs. In contrast, disordered QWs show complexities in the ways of conductance resonance, peak splitting and trace crossing in source-drain bias spectroscopies. The experimental results and theoretical predictions are in congruence. Moreover, the resonant state arising from the impurities results in either a single peak or double-splitting peaks in the spectroscopies from the detailed impurity configurations. The resonant splitting peaks are found to influence the ZBA, indicating that a clean QW is crucial for investigating the intrinsic characteristics of the ZBA of QWs.
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Affiliation(s)
- K M Liu
- Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan
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