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

We present both the experimental and theoretical investigations of a nontrivial electron Landau-level 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 six-band Kane model; then using semiclassical calculations, we showed this behavior is due to the mixing of the conduction band with a total spin of 3/2 with the next well subband with a spin of 1/2, which reduces the average vertical spin from 3/2 to around 1. This change in the average spin changes the Berry phase, explaining the evolution of Landau levels under magnetic field.