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Colloquium:Quantum Spin Hall and Superfluidity in Coupled Electron-Hole Double Layers

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Rui Rui Du, Rice University
When
07 September 2017 from 4:00 PM to 5:00 PM
Where
117 Osmond Laboratory
Contact Name
Jun Zhu
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The last decade has seen a phenomenal rise of topological insulators and superconductors. The first discovery concerns a planar material of a "quantum spin Hall topological insulator", the narrow edges in its perimeters acting as an electronic superhighway. It is one of the building blocks needed to create future electronics and computers. In this talk I will show such insulators can be built from common compound semiconductors containing a double-layer of electrons and holes, being created by band-gap engineering using molecular beam epitaxy and electrostatic gates. The material supports quantized one-dimensional helical edge modes, where the spin orientation and the momentum of the edge mode are locked together by time-reversal symmetry. According to the single particle theory, the edge modes can transport electrical currents without dissipation. Quite surprisingly here we find a superhighway with some puzzling twists, for which electron-electron interactions may be responsible. Amazingly, our recent optical and transport experiments confirm that the material can host a superfluid where the pairing of electron and holes resembles the Cooper pairs in ordinary superconductors. 

Reference:

1. X. C. Liu, T. L. Hughes, X. L. Qi, K. Wang, and S. C. Zhang, Quantum Spin Hall effect in inverted type-II semiconductors. Phys. Rev. Lett. 100, 236601 (2008).

2. L. J. Du. I. Knez. G. Sullivan, R.R. Du, Robust helical edge transport in gated InAs/GaSb bilayers. Phys. Rev. Lett. 114, 096802 (2015).

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