Realistic picture of helical edge states in HgTe quantum wells

TL;DR

This paper introduces a minimal effective Hamiltonian for HgTe quantum wells that better captures the properties of helical edge states, especially considering side maxima, and highlights differences from the BHZ model.

Contribution

It presents a new simplified Hamiltonian for HgTe QWs that accounts for side maxima and explores edge states beyond the traditional BHZ model.

Findings

Edge state dispersion and density differ from BHZ predictions.

The model applies to both tensile and compressively strained HgTe QWs.

Results facilitate further theoretical studies of HgTe-based topological insulators.

Abstract

We propose a minimal effective two-dimensional Hamiltonian for HgTe/CdHgTe quantum wells (QWs) describing the side maxima of the first valence subband. By using the Hamiltonian, we explore the picture of helical edge states in tensile and compressively strained HgTe QWs. We show that both dispersion and probability density of the edge states can differ significantly from those predicted by the Bernevig-Hughes-Zhang (BHZ) model. Our results pave the way towards further theoretical investigations of HgTe-based quantum spin Hall insulators with direct and indirect band gaps beyond the BHZ model.