Topological charge pumping in excitonic insulators

TL;DR

This paper demonstrates that electric fields can induce topological charge pumping in excitonic insulators by rotating the order parameter in the complex plane, leading to quantized electron transport.

Contribution

It reveals a novel mechanism for topological charge pumping in excitonic insulators through electric-field-induced order parameter rotation.

Findings

Each cycle pumps exactly two electrons in 1D systems.

Higher dimensions can be viewed as multiple 1D charge pumping channels.

Dissipative effects beyond the adiabatic limit are discussed.

Abstract

We show that in excitonic insulators with $s$-wave electron-hole pairing, an applied electric field (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.