Symmetry properties of n-doped (Cd,Mn)Te quantum well photoluminescence spectra: An exemplary evidence for anisotropy-induced valence-band mixing

Abstract

The symmetry properties of photoluminescence spectra of an n-doped (001)-Cd0.99Mn0.01Te quantum well provide a simple and intuitive demonstration of the valence-band mixing induced by spontaneous in-plane anisotropy of the sample. The spectra were taken with linear-polarization resolution in an in-plane external magnetic field. They consisted of several features which are characteristic for a two-dimensional electron gas. Because the quantum well layer contained “magnetic” ions of Mn, the spectra showed pronounced polarization-dependent modifications induced by the magnetic field. With the field applied, a 90° rotation of the sample about the surface normal axis resulted in a clearly different spectrum, meaning that the nominally equivalent [110] and [11¯0] in-plane directions in the sample are not equivalent in fact. But, remarkably, the additional 90° rotations of both the polarizer and the analyzer restored the initial spectrum. This combined invariance regarding simultaneous 90° 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 an intermixing of valence subbands leading to a pseudoisotropic g-factor of the ground-state holes.