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DESCRIPTION:Charlie Kane \, U. Penn\n\nA topological insulator is a materia
l with a bulk excitation gap generated by the spin orbit interaction\, whi
ch is topologically distinct from an ordinary insulator. This distinction
- characterized by a topological invariant - necessitates the existence
of gapless metallic states on the sample boundary\, which have important i
mplications for electronic\ntransport. In two\ndimensions\, the topologi
cal insulator is a quantum spin Hall insulator\, which\nis a close cousin
of the integer quantum Hall state. In this talk we\nwill\noutline our th
eoretical discovery of this phase and describe two recent experiments in w
hich the signatures of this effect have been observed. (1) Transport expe
riments on HgTe/HgCdTe quantum wells have demonstrated the existence of th
e edge states predicted for the quantum spin Hall insulator.\n(2) Photoemi
ssion experiments on the semiconducting alloy Bi_{1-x} Sb_x have observed
the signature of the gapless surface states predicted for a three dimensio
nal topological insulator. We will close by arguing that the proximity ef
fect between an ordinary superconductor and a 3D topological insulator lea
ds to a novel two dimensional interface state which may provide a new venu
e for realizing proposals for topological quantum computation.\n
DTSTART:20090123T210000Z
LOCATION:Physics Building\, Room 204
SUMMARY:The Quantum Spin Hall Effect and Topological Band Theory
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