Cornell University

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Friday, December 12, 2014 at 11:00am to 12:00pm

Physical Sciences Building, 416
245 East Avenue

Evelyn Tang, Department of Physics, MIT. Professor Eun-Ah Kim, host.

Seminar Title: Stran-induced partially flat band, helical snake states and interface superconductivity in topological crystalline insulators

Abstract: Topological crystalline insulators in IV-VI compounds host novel topological surface states consisting of multi-valley massless Dirac fermions at low energy. Here we show that strain generically acts as an effective gauge field on these Dirac fermions and creates pseudo-Landau orbitals without breaking time-reversal symmetry. We predict the realization of this phenomenon in IV-VI semiconductor heterostructures, due to a naturally occurring misfit dislocation array at the interface that produces a periodically varying strain field. Remarkably, the zero-energy Landau orbitals form a flat band in the vicinity of the Dirac point, and coexist with a network of snake states at higher energy. We propose that the high density of states of this flat band gives rise to interface superconductivity observed in IV-VI semiconductor multilayers at unusually high temperatures, with non-BCS behavior.

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Douglas E. Milton, Sr.

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Evelyn Tang

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