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Published February 13, 2009 | Supplemental Material
Journal Article Open

Observation of Unconventional Quantum Spin Textures in Topological Insulators

Abstract

A topologically ordered material is characterized by a rare quantum organization of electrons that evades the conventional spontaneously broken symmetry–based classification of condensed matter. Exotic spin-transport phenomena, such as the dissipationless quantum spin Hall effect, have been speculated to originate from a topological order whose identification requires a spin-sensitive measurement, which does not exist to this date in any system. Using Mott polarimetry, we probed the spin degrees of freedom and demonstrated that topological quantum numbers are completely determined from spin texture–imaging measurements. Applying this method to Sb and Bi_(1–x)Sb_x, we identified the origin of its topological order and unusual chiral properties. These results taken together constitute the first observation of surface electrons collectively carrying a topological quantum Berry's phase and definite spin chirality, which are the key electronic properties component for realizing topological quantum computing bits with intrinsic spin Hall–like topological phenomena.

Additional Information

© 2009 American Association for the Advancement of Science. Received for publication 27 October 2008. Accepted for publication 7 January 2009. We thank J. Teo for providing the SS band calculations of antimony (Sb); A. Fedorov, L. Patthey, and D.-H. Lu for beamline assistance; and D. Haldane, B. I. Halperin, N. P. Ong, D. A. Huse, F. Wilczek, P. W. Anderson, D. C. Tsui, J. E. Moore, L. Fu, L. Balents, D.-H. Lee, S. Sachdev, P. A. Lee, and X.-G. Wen for stimulating discussions. C.L.K. was supported by NSF grant DMR-0605066. The spin-resolved ARPES experiments are supported by NSF through the Center for Complex Materials (DMR-0819860) and Princeton University; the use of synchrotron X-ray facilities (ALS-LBNL, Berkeley, and SSRL-SLAC, Stanford) is supported by the Basic Energy Sciences of the U.S. Department of Energy (DE-FG-02–05ER46200) and by the Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland.

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