Magneto-optical four-wave-mixing studies of an exciton-biexciton system in a CdMnTe/CdTe/CdMgTe single quantum well

摘要

Exciton and biexciton states in a CdMnTe/CdTe/CdMgTe quantum well were investigated by means of polarization-dependent four-wave mixing (FWM) measurements in magnetic fields up to 7T. In co-linear and cross-linear polarization geometry, the FWM signals were strongly modified by the magnetic field, which was directed normal to the quantum-well plane. Very clear beat structures due to giant Zeeman splitting of the excitons were observed. In the co-circular (sigma+, sigma+) configuration, a high magnetic field induced a beat-like structure in an early delay-time region. Spectrally resolved FWM signals indicating an additional transition appeared at the 1.1 meV higher energy side of the exciton resonance. According to the spin selection rule, the oscillator strength of the triplet biexciton that consisted of two sigma+ excitons was found to increase in magnetic fields.