Spin mixing between subbands and extraordinary Landau levels shift in wide HgTe quantum wells

TL;DR

This paper investigates the unusual Landau level shifts in wide HgTe quantum wells, revealing spin mixing effects that alter the Berry phase and cause Landau levels to split and recombine under magnetic fields.

Contribution

The study combines experimental data with theoretical models to explain the Landau level behavior through conduction band and subband mixing in wide HgTe quantum wells.

Findings

Landau levels split and recombine with increasing magnetic field.

Spin mixing reduces average vertical spin from 3/2 to about 1.

Berry phase change accounts for Landau level evolution.

Abstract

We present both the experimental and theoretical investigation of a non-trivial electron Landau levels shift in magnetic field in wide ~20 nm HgTe quantum wells: Landau levels split under magnetic fields but become degenerate again when magnetic field increases. We reproduced this behavior qualitatively within an isotropic 6-band Kane model, then using semiclassical calculations we showed this behavior is due to the mixing of the conduction band with total spin 3/2 with the next well subband with spin 1/2 which reduces the average vertical spin from 3/2 to around 1. This change of the average spin changes the Berry phase explaining the evolution of Landau levels under magnetic field.