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A topological Dirac insulator in a quantum spin Hall phase

Hsieh, D. and Qian, D. and Wray, L. and Xia, Y. and Hor, Y. S. and Cava, R. J. and Hasan, M. Z. (2008) A topological Dirac insulator in a quantum spin Hall phase. Nature, 452 (7190). pp. 970-974. ISSN 0028-0836. doi:10.1038/nature06843.

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When electrons are subject to a large external magnetic field, the conventional charge quantum Hall effect dictates that an electronic excitation gap is generated in the sample bulk, but metallic conduction is permitted at the boundary. Recent theoretical models suggest that certain bulk insulators with large spin–orbit interactions may also naturally support conducting topological boundary states in the quantum limit, which opens up the possibility for studying unusual quantum Hall-like phenomena in zero external magnetic fields. Bulk Bi_(1-x)Sb_x single crystals are predicted to be prime candidates for one such unusual Hall phase of matter known as the topological insulator. The hallmark of a topological insulator is the existence of metallic surface states that are higher-dimensional analogues of the edge states that characterize a quantum spin Hall insulator. In addition to its interesting boundary states, the bulk of Bi_(1-x)Sb_x is predicted to exhibit three-dimensional Dirac particles, another topic of heightened current interest following the new findings in two-dimensional graphene and charge quantum Hall fractionalization observed in pure bismuth. However, despite numerous transport and magnetic measurements on the Bi_(1-x)Sb_x family since the 1960s, no direct evidence of either topological Hall states or bulk Dirac particles has been found. Here, using incident-photon-energy-modulated angle-resolved photoemission spectroscopy (IPEM-ARPES), we report the direct observation of massive Dirac particles in the bulk of Bi_(0.9)Sb_(0.1), locate the Kramers points at the sample's boundary and provide a comprehensive mapping of the Dirac insulator's gapless surface electron bands. These findings taken together suggest that the observed surface state on the boundary of the bulk insulator is a realization of the 'topological metal'. They also suggest that this material has potential application in developing next-generation quantum computing devices that may incorporate 'light-like' bulk carriers and spin-textured surface currents.

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Hsieh, D.0000-0002-0812-955X
Additional Information:© 2008 Nature Publishing. Received 25 November 2007; Accepted 14 February 2008. We thank P. W. Anderson, B. A. Bernevig, L. Balents, E. Demler, A. Fedorov, F. D. M. Haldane, D. A. Huse, C. L. Kane, R. B. Laughlin, J. E. Moore, N. P. Ong, A. N. Pasupathy, D. C. Tsui and S.-C. Zhang for discussions. The synchrotron experiments are supported by the DOE-BES and materials synthesis is supported by the NSF-MRSEC at Princeton Center for Complex Materials.
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Department of Energy (DOE)UNSPECIFIED
Issue or Number:7190
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Official Citation:A topological Dirac insulator in a quantum spin Hall phase D. Hsieh, D. Qian, L. Wray, Y. Xia, Y. S. Hor, R. J. Cava & M. Z. Hasan Nature 452, 970-974 (24 April 2008) doi:10.1038/nature06843
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49766
Deposited By: Tony Diaz
Deposited On:18 Sep 2014 03:12
Last Modified:10 Nov 2021 18:47

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