Effects of electron-hole asymmetry on electronic structure of helical edge states in HgTe/HgCdTe quantum wells

TL;DR

This paper investigates how electron-hole asymmetry and lack of inversion symmetry influence the electronic structure of helical edge states in HgTe/HgCdTe quantum wells, providing analytical models and identifying spectrum deviations.

Contribution

It introduces analytical expressions for edge state spectra and wave functions considering electron-hole asymmetry and inversion asymmetry in HgTe/HgCdTe quantum wells.

Findings

Edge electron spectrum deviates from linearity under combined asymmetry and inversion absence.

Derived analytical formulas for energy spectrum and wave functions of edge states.

Identified corrections to the linear spectrum due to asymmetry effects.

Abstract

We study the effects of electron-hole asymmetry on the electronic structure of helical edge states in HgTe/HgCdTe quantum wells. In the framework of the four-band kp-model, which takes into account the absence of a spatial inversion centre, we obtain analytical expressions for the energy spectrum and wave functions of edge states, as well as the effective g-factor tensor and matrix elements of electro-dipole optical transitions between the spin branches of the edge electrons. We show that when two conditions are simultaneously satisfied -- electron-hole asymmetry and the absence of an inversion centre -- the spectrum of edge electrons deviates from the linear one, in that case we obtain corrections to the linear spectrum.