Special CM Seminar, Aris Alexandradinata, Yale, "The first nonsymmorphic topological insulator: prediction and discovery"

Jun 8, 2016, 1:30 pm3:00 pm
Jadwin A07
Event Description
Spatial symmetries in crystals are distinguished by whether they preserve the spatial origin. I will show how this basic geometric property gives rise to a new topology in band insulators, which we propose (and subsequently discover) to lie in the large-gap insulators: KHgX (X=As,Sb,Bi). These insulators are described by generalized symmetries that combine space-time transformations with quasimomentum translations in the Brillouin torus. This provides a natural generalization of space groups, such that real and quasimomentum spaces are placed on equal footing. A broader consequence of our theory is a connection between band topology and group cohomology. References: Nature 532, 189-194, Phys. Rev. X 6, 021008