Effect of magnetoexciton correlations on the coherent emission of semiconductors

Abstract

Mean-field, Hartree-Fock theory has been successful in explaining many nonlinear optical experiments in semiconductors. But recently experiments have shown important cases where the mean-field theory ͑the semiconductor Bloch equations͒ fails. One such case is bulk GaAs in a strong magnetic field. Here the excitonexciton interaction can be tuned by varying the magnetic field, providing an excellent method for studying the transition from a regime where mean-field theory is valid to a regime where exciton-exciton correlations must be taken into account. We perform ultrafast time-resolved four-wave mixing on bulk GaAs in a magnetic field, and compare our experimental results with theoretical calculations which go beyond Hartree-Fock theory. We find excellent qualitative agreement. Furthermore, because of the strong correlations that are present, GaAs in a magnetic field presents an excellent opportunity to study the exciton-exciton correlations themselves. We investigate the coherence of the exciton-exciton correlations as the temperature and free-carrier density are varied, and find a surprising sensitivity of the exciton-exciton correlation coherence to these parameters.

Wavefunction analysis and optical nutation in magnetized semiconductor quantum wires exhibiting multiple valence subbands

“…The light holes give rise to higher frequency oscillation with larger amplitude and heavy holes with lower frequency oscillations modulate the light hole signal, giving rise to multiple oscillations. Similar feature was demonstrated experimentally by Kner et al [33] and Albrecht et al [34] in their work on quantum wells. Schmitt-Rink et al [35] and Garro et al [36] reported experimental observation of heavy-and light-hole beating in GaAs/ AlGaAs QWs.…”

Many-body and correlation effects in semiconductors

“…Thus it is stored in the medium until the second pulse triggers that emission. This`coherent memory' can be interpreted as a non-markovian process involving the 2-particle correlation polarization waves interacting with a bath of 4-particle correlations 36 . The effects of 4-particle correlations have been shown to be important in other recent experiments as well 7 .…”

Semiconductor polarization dynamics from the coherent to the incoherent regime: Theory and experiment

“…In other systems, such as magnetoexcitons in bulk GaAs, this rise time can become much longer than the decay time. 39,18 Experimentally we found that, in the range of density explored here, the decay time decreases by a factor of 2 following approximately the relation T 2 Ϫ1 ϰN cw 0.15 , see the solid symbols in Fig. 6.…”