Seminar - Dr. Ce Shang

Seminar: "Quantum anomalous Hall-quantum spin Hall effect and Weyl soliton in optical lattices​"
Ce Shang, Ph.D.

November 26th, 2018
B3/L5/R5209 at 2 p.m.

Quantum spin Hall effect and quantum anomalous Hall effect are both fundamental transport processes in topological insulators. However, realizing these two effects in one system is difficult due to fact that the former requires protecting time reversal symmetry while the latter needs broken time reversal symmetry. Here we put forward a new category of topological insulators, which possessing quantum spin Hall phase in one gap and simultaneously possessing anomalous Hall phase in others. This uncovered matter of state may contain interesting applications in topological physics.
Weyl fermions are massless chiral quasiparticles existing in materials known as Weyl semimetals. Topological surface states, associated with the unusual electronic structure in the Weyl semimetals, have been recently demonstrated in linear systems. In this work, we report, for the first time to our knowledge, the existence of localized Weyl solitons in the three-dimensional (3D) optical lattice. We unprecedentedly built the effective 3D model with an embedded nonlinearity, and show that Weyl solitons travel robustly along the surface over a very long time interval. We expect the suggested model of the nonlinear optical Weyl lattice opens a new frontier of nonlinear Weyl physics and conquer the difficulty of physical realization in the real material. This scheme may offer an efficient control of quasi-excitations in condensed-matter physics, which may be used for undistorted signal transmission. Weyl solitons, following the very recently reported Dirac solitons and Majorana solitons, constitute the third and also the last member in the family of topological solitons.
We perform these two novel phenomena in the optical lattice to build linear and nonlinear model to reveal underlying physics. These proposals may offer novel routes to control the topological transportation.