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Imaging current distribution in a topological insulator Bi 2Se 3 in the presence of competing surface and bulk contributions to conductivity. Sci Rep 2021; 11:7445. [PMID: 33811220 PMCID: PMC8018954 DOI: 10.1038/s41598-021-86706-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 03/15/2021] [Indexed: 11/10/2022] Open
Abstract
Two-dimensional (2D) topological surface states in a three-dimensional topological insulator (TI) should produce uniform 2D surface current distribution. However, our transport current imaging studies on Bi2Se3 thin film reveal non-uniform current sheet flow at 15 K with strong edge current flow. This is consistent with other imaging studies on thin films of Bi2Se3. In contrast to strong edge current flow in thin films, in single crystal of Bi2Se3 at 15 K our current imaging studies show the presence of 3.6 nm thick uniform 2D sheet current flow. Above 70 K, this uniform 2D sheet current sheet begins to disintegrate into a spatially non-uniform flow. The flow becomes patchy with regions having high and low current density. The area fraction of the patches with high current density rapidly decreases at temperatures above 70 K, with a temperature dependence of the form \documentclass[12pt]{minimal}
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\begin{document}$$1/\left| {T - 70} \right|^{0.35}$$\end{document}1/T-700.35. The temperature scale of 70 K coincides with the onset of bulk conductivity in the crystal due to electron doping by selenium vacancy clusters in Bi2Se3. Thus our results show a temperature dependent competition between surface and bulk conductivity produces a temperature dependent variation in uniformity of current flow in the topological insulator.
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Li L, Wang Y, Wang Z, Liu Y, Wang B. Topological Insulator GMR Straintronics for Low-Power Strain Sensors. ACS APPLIED MATERIALS & INTERFACES 2018; 10:28789-28795. [PMID: 30058327 DOI: 10.1021/acsami.8b09664] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A quantum spin Hall insulator, i.e., topological insulator (TI), is a natural candidate for low-power electronics and spintronics because of its intrinsic dissipationless feature. Recent density functional theory and scanning tunneling spectroscopy experiments show that the mechanical strain allows dynamic, continuous, and reversible modulations of the topological surface states within the topological phase and hence opens prospects for TI straintronics. Here, we combine the mechanical strain and the giant magnetoresistance (GMR) of a ferromagnet-TI (FM-TI) junction to construct a novel TI GMR straintronics device. Such a FM-strained-FM-TI junction permits several energy spectral ranges for 100% GMR and a robust strain-controllable magnetic switch. Beyond the 100% GMR energy range, we observe a strain-modulated oscillating GMR, which is an alternative hallmark of the Fabry-Pérot quantum interference of Dirac surface states. These strain-sensitive GMR responses indicate that FM-strained-FM-TI junctions are very favorable for practical applications for low-power nanoscale strain sensors.
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Affiliation(s)
- Lingzhi Li
- School of Engineering , Sun Yat-sen University , Guangzhou 510006 , China
| | - Yunhua Wang
- Sino-French Institute of Nuclear Engineering and Technology , Sun Yat-sen University , Zhuhai 519082 , China
- State Key Laboratory of Optoelectronic Materials and Technologies , Sun Yat-sen University , Guangzhou 510275 , China
| | - Zongtan Wang
- School of Engineering , Sun Yat-sen University , Guangzhou 510006 , China
| | - Yulan Liu
- School of Engineering , Sun Yat-sen University , Guangzhou 510006 , China
| | - Biao Wang
- Sino-French Institute of Nuclear Engineering and Technology , Sun Yat-sen University , Zhuhai 519082 , China
- State Key Laboratory of Optoelectronic Materials and Technologies , Sun Yat-sen University , Guangzhou 510275 , China
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Yeats AL, Mintun PJ, Pan Y, Richardella A, Buckley BB, Samarth N, Awschalom DD. Local optical control of ferromagnetism and chemical potential in a topological insulator. Proc Natl Acad Sci U S A 2017; 114:10379-10383. [PMID: 28900003 PMCID: PMC5625936 DOI: 10.1073/pnas.1713458114] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many proposed experiments involving topological insulators (TIs) require spatial control over time-reversal symmetry and chemical potential. We demonstrate reconfigurable micron-scale optical control of both magnetization (which breaks time-reversal symmetry) and chemical potential in ferromagnetic thin films of Cr-(Bi,Sb)2Te3 grown on SrTiO3 By optically modulating the coercivity of the films, we write and erase arbitrary patterns in their remanent magnetization, which we then image with Kerr microscopy. Additionally, by optically manipulating a space charge layer in the underlying SrTiO3 substrates, we control the local chemical potential of the films. This optical gating effect allows us to write and erase p-n junctions in the films, which we study with photocurrent microscopy. Both effects are persistent and may be patterned and imaged independently on a few-micron scale. Dynamic optical control over both magnetization and chemical potential of a TI may be useful in efforts to understand and control the edge states predicted at magnetic domain walls in quantum anomalous Hall insulators.
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Affiliation(s)
- Andrew L Yeats
- Institute for Molecular Engineering, University of Chicago, Chicago, IL 60637
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439
| | - Peter J Mintun
- Institute for Molecular Engineering, University of Chicago, Chicago, IL 60637
| | - Yu Pan
- Materials Research Institute, The Pennsylvania State University, University Park PA 16802
- Department of Physics, The Pennsylvania State University, University Park PA 16802
| | - Anthony Richardella
- Materials Research Institute, The Pennsylvania State University, University Park PA 16802
- Department of Physics, The Pennsylvania State University, University Park PA 16802
| | - Bob B Buckley
- Institute for Molecular Engineering, University of Chicago, Chicago, IL 60637
| | - Nitin Samarth
- Materials Research Institute, The Pennsylvania State University, University Park PA 16802
- Department of Physics, The Pennsylvania State University, University Park PA 16802
| | - David D Awschalom
- Institute for Molecular Engineering, University of Chicago, Chicago, IL 60637;
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439
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Uri A, Meltzer AY, Anahory Y, Embon L, Lachman EO, Halbertal D, Hr N, Myasoedov Y, Huber ME, Young AF, Zeldov E. Electrically Tunable Multiterminal SQUID-on-Tip. NANO LETTERS 2016; 16:6910-6915. [PMID: 27672705 DOI: 10.1021/acs.nanolett.6b02841] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We present a new nanoscale superconducting quantum interference device (SQUID) whose interference pattern can be shifted electrically in situ. The device consists of a nanoscale four-terminal-four-junction SQUID fabricated at the apex of a sharp pipet using a self-aligned three-step deposition of Pb. In contrast to conventional two-terminal-two-junction SQUIDs that display optimal sensitivity when flux biased to about a quarter of the flux quantum, the additional terminals and junctions allow optimal sensitivity at arbitrary applied flux, thus eliminating the magnetic field "blind spots". We demonstrate spin sensitivity of 5 to 8 μB/Hz1/2 over a continuous field range of 0 to 0.5 T with promising applications for nanoscale scanning magnetic imaging.
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Affiliation(s)
- Aviram Uri
- Department of Condensed Matter Physics, Weizmann Institute of Science , Rehovot 7610001, Israel
| | - Alexander Y Meltzer
- Department of Condensed Matter Physics, Weizmann Institute of Science , Rehovot 7610001, Israel
| | - Yonathan Anahory
- Department of Condensed Matter Physics, Weizmann Institute of Science , Rehovot 7610001, Israel
| | - Lior Embon
- Department of Condensed Matter Physics, Weizmann Institute of Science , Rehovot 7610001, Israel
| | - Ella O Lachman
- Department of Condensed Matter Physics, Weizmann Institute of Science , Rehovot 7610001, Israel
| | - Dorri Halbertal
- Department of Condensed Matter Physics, Weizmann Institute of Science , Rehovot 7610001, Israel
| | - Naren Hr
- Department of Condensed Matter Physics, Weizmann Institute of Science , Rehovot 7610001, Israel
| | - Yuri Myasoedov
- Department of Condensed Matter Physics, Weizmann Institute of Science , Rehovot 7610001, Israel
| | - Martin E Huber
- Department of Condensed Matter Physics, Weizmann Institute of Science , Rehovot 7610001, Israel
- Departments of Physics and Electrical Engineering, University of Colorado , Denver, Colorado 80217, United States
| | - Andrea F Young
- Department of Condensed Matter Physics, Weizmann Institute of Science , Rehovot 7610001, Israel
- Department of Physics, University of California , Broida Hall, Santa Barbara, California 93106, United States
| | - Eli Zeldov
- Department of Condensed Matter Physics, Weizmann Institute of Science , Rehovot 7610001, Israel
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Sumiyoshi H, Fujimoto S. Torsional Chiral Magnetic Effect in a Weyl Semimetal with a Topological Defect. PHYSICAL REVIEW LETTERS 2016; 116:166601. [PMID: 27152814 DOI: 10.1103/physrevlett.116.166601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Indexed: 06/05/2023]
Abstract
We propose a torsional response raised by a lattice dislocation in Weyl semimetals akin to a chiral magnetic effect; i.e., a fictitious magnetic field arising from a screw or edge dislocation induces a charge current. We demonstrate that, in sharp contrast to the usual chiral magnetic effect that vanishes in real solid state materials, the torsional chiral magnetic effect exists even for realistic lattice models, which implies the experimental detection of the effect via superconducting quantum interference device or nonlocal resistivity measurements in Weyl semimetal materials.
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Affiliation(s)
| | - Satoshi Fujimoto
- Department of Materials Engineering Science, Osaka University, Toyonaka 560-8531, Japan
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Wang YH, Kirtley JR, Katmis F, Jarillo-Herrero P, Moodera JS, Moler KA. Retraction. Observation of chiral currents at the magnetic domain boundary of a topological insulator. Science 2015; 350:1482. [PMID: 26680185 DOI: 10.1126/science.350.6267.1482-a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Y. H. Wang
- Department of Physics and Applied Physics, Stanford University, Stanford, CA 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - J. R. Kirtley
- Department of Physics and Applied Physics, Stanford University, Stanford, CA 94305, USA
| | - F. Katmis
- Francis Bitter Magnet Laboratory and Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - P. Jarillo-Herrero
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - J. S. Moodera
- Francis Bitter Magnet Laboratory and Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - K. A. Moler
- Department of Physics and Applied 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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