Axion insulators and topological chiral hinge states protected by inversion symmetry
In this talk I theoretically study axion insulators, which are also known as higher-order topological insulators. This phase is a topological phase protected by inversion symmetry but without time-reversal symmetry. In such systems, hinge states are known to appear along hinges of the crystals. Here we discuss how the appearance of hinge states results from the bulk Z4 topological number. Furthermore, we show how the positions of the hinge states are determined in systems under various symmetries. In particular we apply our theory to a layered antiferromagnet such as EuIn2As2 to show that the positions of hinge states show novel dependence on the parity of the number of layers. If the time allows, I also introduce our recent research on nonhermitian systems. In nonhermitian systems, we recently establish Bloch band theory in crystals, and show that the Brillouin zone acquires various new properties such as presence of cusps, as compared with Hermitian cases.
Chair: Yong-Baek Kim (KIAS/University of Toronto)
Note : This event is jointly organized by the Korea Institute for Advanced Study and the University of Tokyo. “Correlated Electrons Virtual International Seminars (CEVIS)” https://sites.google.com/view/cevis2020/home