CCQ Seminar: Zhiyuan Sun

Tuesday Aug 25, 2020, 12:00 PM → 1:00 PM America/New_York

Title: Topological charge pumping in excitonic insulators.

Abstract:Photo-induced dynamics of symmetry broken phases contains rich physics. We show that in excitonic insulators with s-wave electron-hole pairing, subdominant order parameter fluctuations in the p-wave channel exist as Bardasis-Schrieffer polaritons and can be excited by weak electric fields. Stronger fields (either pulsed or static) can induce a p-wave component to the order parameter, and further drive it to rotate in the s+ip plane, realizing a Thouless charge pump. In one dimension, each cycle of rotation pumps exactly two electrons across the sample. Higher dimensional systems can be viewed as a stack of one dimensional chains in momentum space in which each chain crossing the fermi surface contributes a channel of charge pumping. Physics beyond the adiabatic limit, including in particular dissipative effects is discussed.