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[资源] 【资源】《Nature》2009年8月27日出品内容

《Nature》2009年8月27日出品内容
》》》》》》》》》》》》》》》》》》》》》
Topological surface states protected from backscattering by chiral spin texture
Pedram Roushan1, Jungpil Seo1, Colin V. Parker1, Y. S. Hor2, D. Hsieh1, Dong Qian1, Anthony Richardella1,M. Z. Hasan1, R. J. Cava2& Ali Yazdani1
Topological insulators are a new class of insulators in which a bulk
gap for electronic excitations is generated because of the strong
spin–orbit coupling1–5
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
structures6–8
and several bismuth-based compounds9–13
, 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
Bi12xSbx, 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
14
, and also for quantum computing applica-
tions, where topological protection can enable fault-tolerant
information processing15,16
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