Speaker: Aris Alexandradinata
Affiliation: Princeton University, USA
Abstract Details: 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.Click HERE for directions

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