Topological edge-state contributions to high-order harmonic generation in finite flakes

TL;DR

This paper investigates how topological edge states influence high-harmonic generation in finite flakes of a 2D topological insulator modeled by the Haldane model, revealing size-dependent spectral features.

Contribution

It demonstrates the significant role of edge states in HHG spectra and explains size-dependent spectral peaks using edge state dispersion relations.

Findings

Edge states cause additional peaks in HHG spectra below the bulk band gap.

Spectral peak positions depend strongly on the size of the flakes.

Edge state contributions can be distinguished from bulk responses in HHG.

Abstract

Edge states play a major role in the electron dynamics of topological insulators as they are the only conducting part in such materials. In this work, we consider the Haldane model for a 2D topological insulator, subjected to an intense laser field. We compare the numerically simulated high-harmonic generation (HHG) in the bulk of the Haldane model to HHG in corresponding finite flakes with edge states present, and explain the differences. In particular, peaks for energies below the bulk band gap appear in the spectra for the finite flakes. The positions of these peaks show a strong dependence on the size of the flakes, which can be explained using the dispersion relation for the edge states.