LUMINESCENCE POLARIZATION AND SPONTANEOUS LOWERING OF SYMMETRY CAUSEDBY MAGNETIC-POLARON FORMATION IN SEMIMAGNETIC-SEMICONDUCTOR QUANTUM-WELLS

An experimental and theoretical study of the magnetic polaron states o f two-dimensional excitons in quantum wells based on semimagnetic semi conductors (Cd,Mn)Te is reported. It is shown that magnetic-polaron fo rmation 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 fi eld and contains a component normal to the quantum-well plane. This sp ontaneous lowering of the symmetry results in a change of the polariza tion characteristics of the luminescence from magnetic polaron states and in a weakening (compared to the three-dimensional case) in the eff iciency of magnetic field-induced polaron suppression. (C) 1997 Americ an Institute of Physics.