Seminar：Topological Dirac Insulators

Time: 10:30 am, August 16, 2017

Location: Room 242, East 4 teaching building, Zijingang Campus

Dr. Zhijun Wang

Princeton University

Abstract

This discovery of symmetry-protected states of matters has attracted tremendous interest in a wide range of areas from condensed matter physics to materials science and high-energy physics. The first discovered TI[1] is protected by time-reversal symmetry with Kramers degeneracy protecting nontrivial conducting states on the boundary. Then, the classification of topological insulating phases has been extended to many other discrete symmetry classes, like topological crystalline insulators[2], hourglass fermions[3, 4] and Dirac insulators[5]. We study the non-interacting topological phases allowed in bulk crystals with surfaces invariant under the certain symmetries. We show that topological Dirac insulators host a novel topological phases characterized by a single, symmetry-enforced fourfold Dirac fermion on the surface, i.e., twice the degeneracy of a traditional topological insulator surface state.

[1] HJ Zhang, et al. Nature physics 5, 438-442 (2009).

[2] L. Fu, Phys. Rev. Lett. 106, 106802 (20011).

[3] ZJ Wang, A Alexandradinata, et al. Hourglass fermions. Nature 532, 189-194 (2016).

[4] J-Z Ma, C-J Yi, BQ Lv, ZJWang, et al. Science Advances 3, 1602415 (2017).

[5] BJ Wieder, B Bradlyn, ZJ Wang, J Cano, et al. Topological Dirac Insulators, arXiv: 1705. 01617 (2017).