Title: 4D Topological Insulators with Nodal-Line Boundary States

Speaker: Zhao Yuxin

Location: Room 101, Physical science Building

Time: 16:00-17:00p.m. Dec 11th, 2018

Abstract: Conventional topological insulators and superconductors have topologically protected nodal points in their boundaries, and the recent interests in nodal-line semimetals merely concerned bulk band structures. In this talk, we present a novel four-dimensional topological insulator protected by an anti-unitary refection symmetry, whose boundary band has a single PT-symmetric nodal line with double topological charges. The construction of the model is guided by the K-theoretical formulation of the bulk-boundary correspondence of topological insulators. Fascinatingly, the Z2 bulk topological invariant is formulated as the second Chern number over a half Brilliance zone subtracted by Chern-Simons integrals over its boundaries, and therefore can be regarded as a four-dimensional generalization of the topological invariant of 2D time-reversal-invariant topological insulators. A cold-atom realization proposal will also be briefly discussed.