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Topological surface states protected from backscattering by chiral spin texture

Roushan, Pedram and Seo, Jungpil and Parker, Colin V. and Hor, Y. S. and Hsieh, D. and Qian, Dong and Richardella, Anthony and Hasan, M. Z. and Cava, R. J. and Yazdani, Ali (2009) Topological surface states protected from backscattering by chiral spin texture. Nature, 460 (7259). pp. 1106-1109. ISSN 0028-0836. doi:10.1038/nature08308.

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Topological insulators are a new class of insulators in which a bulk gap for electronic excitations is generated because of the strong spin–orbit coupling inherent to these systems. These materials are distinguished from ordinary insulators by the presence of gapless metallic surface states, resembling chiral edge modes in quantum Hall systems, but with unconventional spin textures. A key predicted feature of such spin-textured boundary states is their insensitivity to spin-independent scattering, which is thought to protect them from backscattering and localization. Recently, experimental and theoretical efforts have provided strong evidence for the existence of both two- and three-dimensional classes of such topological insulator materials in semiconductor quantum well structures and several bismuth-based compounds, but so far experiments have not probed the sensitivity of these chiral states to scattering. Here we use scanning tunnelling spectroscopy and angle-resolved photoemission spectroscopy to visualize the gapless surface states in the three-dimensional topological insulator Bi_(1-x)Sb_x, and examine in detail the influence of scattering from disorder caused by random alloying in this compound. We show that, despite strong atomic scale disorder, backscattering between states of opposite momentum and opposite spin is absent. Our observations demonstrate that the chiral nature of these states protects the spin of the carriers. These chiral states are therefore potentially useful for spin-based electronics, in which long spin coherence is critical, and also for quantum computing applications, where topological protection can enable fault-tolerant information processing.

Item Type:Article
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URLURL TypeDescription information
Seo, Jungpil0000-0002-0442-288X
Hsieh, D.0000-0002-0812-955X
Additional Information:© 2014 Macmillan Publishers Limited. Received 13 May 2009; Accepted 21 July 2009; Published online 9 August 2009. We acknowledge K. K. Gomes and A. N. Pasupathy for suggestions about experimental procedure and initial analysis. This work was supported by grants from ONR, ARO, DOE, NSF-DMR and the NSF-MRSEC programme through the Princeton Center for Complex Materials. P.R. acknowledges an NSF graduate fellowship.
Funding AgencyGrant Number
Princeton Center for Complex MaterialsUNSPECIFIED
Office of Naval Research (ONR)UNSPECIFIED
Army Research Office (ARO)UNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
NSF Graduate FellowshipUNSPECIFIED
Issue or Number:7259
Record Number:CaltechAUTHORS:20140911-161926592
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49629
Deposited By: Joy Painter
Deposited On:12 Sep 2014 22:55
Last Modified:10 Nov 2021 18:46

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