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Prof. N. Peter Armitage seminar

Prof. N. Peter Armitage seminar

2013年5月29日

***セミナー***
講演者:
Prof. N. Peter Armitage
Johns Hopkins University

タイトル:
How to kill a topological insulator

アブストラクト:
Topological insulators (TIs) are states of matter characterized by an
inverted band structure driven by strong spin-orbit coupling (SOC). They
have a variety of unusual properties including robust surface states (SS)
that are protected by topological properties of the bulk wavefunctions. Of
particular interest is the quantum phase transition that separates a TI from
a conventional insulator. Such a transition between different topological
classes can only occur when the bulk band gap closes. In this work, we have
utilized time-domain terahertz spectroscopy (TDTS) to investigate the low
frequency conductivity in (Bi1-xInx)2Se3 through this transition by tuning
SOC through In substitution. Above a thickness dependent doping threshold we
observe a sudden collapse in the transport lifetime that indicates the
destruction of the topological phase. We associate this with the doping
where the states from opposite surfaces hybridize. As a function of
thickness this threshold asymptotically approaches the doping x~0.06 of a
maximum in the mid-infrared absorption, which can be identified with the
band gap closing and change in topological class. Our work shows the
fundamental role that finite size effects play in this transition though the
´bulk-boundary correspondence´ of topological systems.

日時:2013年5月29日(水)13時30分から1時間程度
場所:H棟,H701号室

世話人:田中清尚(未来戦略機構)
ktanaka@phys.sci.osaka-u.ac.jp

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