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More surprises in Bismuth, and next-generation spinless topological insulators without time-reversal symmetry

Speaker: 
Aris Alexandradinata (Princeton University, USA)
Date: 
Tue, 09/09/2014 - 2:00pm to 3:00pm
Location: 
S13-M01-11 (Physics Conference Room)
Host: 
Hsin Lin
Event Type: 
Seminars

Abstract

The 2D topological insulator is distinguished from ordinary insulators by the quantum spin Hall effect, which results in an enhanced magnetic susceptibility. Due to its strong diamagnetism, Bismuth is a promising candidate for such a phase of matter. We report the observation of edge states on Bismuth bilayers, which validate theoretical predictions that 2D Bismuth is indeed a topological insulator. Bismuth thus joins a growing list of experimentally-realized topological insulators, which depend essentially on spin-orbit coupling and/or time-reversal symmetry. To move beyond this paradigm, we theoretically propose the first-known 3D topological insulators without spin-orbit coupling, and with surface modes that are protected only by point groups, i.e., not needing time-reversal symmetry. Our findings greatly expand the range of electronic materials that may host topological phases, and has exciting implications for intrinsically spinless systems such as photonic crystals and ultra-cold atoms. If time permits, I will also introduce topological phases of matter without robust boundary states; they are uniquely distinguished by the crystal-analog of Berry phases.

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