Luminescence polarization and spontaneous lowering of symmetry caused by magnetic-polaron formation in semimagnetic-semiconductor quantum wells

An experimental and theoretical study of the magnetic polaron states of two-dimensional excitons in quantum wells based on semimagnetic semiconductors (Cd,Mn)Te is reported. It is shown that magnetic-polaron formation in in-plane magnetic fields leads to a lowering of the system symmetry, provided the fields are not too strong. The magnetic moment of the polaron thus formed is not parallel to the external magnetic field and contains a component normal to the quantum-well plane. This spontaneous lowering of the symmetry results in a change of the polarization characteristics of the luminescence from magnetic polaron states and in a weakening (compared to the three-dimensional case) in the efficiency of magnetic field-induced polaron suppression.