Photoluminescence spectra of an n-doped (Cd,Mn)Te quantum well: an exemplary evidence for the anisotropy-induced valence-band mixing

Photoluminescence spectra of a (001)-Cd0.99Mn0.01Te quantum well were taken with linear-polarization resolution and using an in-plane magnetic field. Because the quantum well contained a two-dimensional electron gas, the spectra consisted of several features. Since the quantum well layer was formed by a diluted magnetic semiconductor, the spectra showed pronounced polarization-dependent transformations when the in-plane magnetic field was applied. In the magnetic field, a 90-degrees rotation of the sample about the surface normal axis resulted in a clearly different spectrum, meaning that the nominally equivalent [110] and [1-10] directions in the sample are not equivalent in fact. But, remarkably, the additional 90-degrees rotations of both the polarizer and the analyzer restored the initial spectrum. This combined invariance regarding simultaneous 90-degrees rotation of the sample and reversal of the polarization configuration was known earlier for spin-flip Raman spectra only. Our present observations are interpreted in terms of the mixing of valence subbands leading to the pseudo-isotropic g-factor of the ground-state holes.