Center for Artificial Low Dimensional Electronic Systems

Z4xZ2 Topological Dirac insulator

YOUNGKUK KIM

September 22(Fri) - September 22(Fri), 2017

Z₄xZ₂ Topological Dirac insulator

YOUNGKUK KIM

Sungkyunkwan University

 Recent development of topological band theory has been the discoveries of diverse topological materials, such as topological insulators, topological crystalline insulators, and topological semimetals. Using nonsymmorphic space group symmetries, we have found a new topological crystalline insulating phase, which we referred to as a topological Dirac insulator [1]. A topological Dirac insulator is a bulk topological crystalline insulator, characterized by a fourfold degenerate surface Dirac points. We introduce topological Dirac insulators, and show that p4g or pgg wallpaper group symmetries, together with time-reversal symmetry, protect fourfold degenerate Dirac points. We also show the presence of the Dirac points is dictated by bulk Z₄xZ₂ topological invariants, calculated from the Wilson loops. Using first-principles calculations, we predict topological Dirac insulators can occur in Sr₂Pb₃ in space group 127.

[1] Wieder, Benjamin J., Barry Bradlyn, Zhijun Wang, Jennifer Cano, Youngkuk Kim, Hyeong-Seok D. Kim, A. M. Rappe, C. L. Kane, and B. Andrei Bernevig. "Wallpaper Fermions and the Topological Dirac Insulator." arXiv preprint arXiv:1705.01617 (2017).