Photon Inhibited Topological Transport in Quantum Well Heterostructures

TL;DR

This paper investigates how periodic driving fields affect topological transport in quantum well heterostructures, revealing photon-induced suppression of conductance while preserving edge state robustness.

Contribution

It introduces a probabilistic framework for understanding photon-assisted topological transport and generalizes existing methods to include the effects of time-dependent driving fields.

Findings

Photon absorption/emission reduces conductance below quantized values.

Edge states remain topologically robust despite transport suppression.

Theoretical interpretation aligns with photon assisted tunneling phenomena.

Abstract

Here we provide a picture of transport in quantum well heterostructures with a periodic driving field in terms of a probabilistic occupation of the topologically protected edge states in the system. This is done by generalizing methods from the field of photon assisted tunneling. We show that the time dependent field {\it dresses} the underlying Hamiltonian of the heterostructure and splits the system into side-bands. Each of these sidebands is occupied with a certain probability which depends on the drive frequency and strength. This leads to a reduction in the topological transport signatures of the system because of the probability to absorb/emit a photon. Therefore when the voltage is tuned to the bulk gap the conductance is smaller then the expected $2e^2/h$. We refer to this as photon inhibited topological transport. Nevertheless, the edge modes reveal their topological origin in the robustness of the edge conductance to disorder and changes in model parameters. In this work the analogy with photon assisted tunneling allows us to interpret the calculated conductivity and explain the sum rule observed by previous authors