Correlation coefficient for dephasing of light-hole excitons and heavy-hole excitons in GaAs quantum wells

摘要

Dephasing of light-hole (LH) and heavy-hole (HH) excitons and of the non-radiative LH-HH exciton Raman coherence in weakly-disordered GaAs quantum wells is probed using three-beam transient four-wave mixing (TFWM). By varying the two inter-pulse delays independently, the radiative inter-band and non-radiative intra-band coherences can be probed independently. A theoretical model based on the density matrix and including inhomogeneous broadening and inhomogeneous dephasing rates is fit to the TFWM data to extract the dephasing rates. The dephasing rate of the LH-HH Raman coherence can be expressed as a function of the dephasing rates of the LH and HH excitons and a correlation coefficient, R-ph, allowing for the calculation of R-ph. We find R-ph < 0, suggesting that anti-correlated scattering dominates the exciton dephasing. (C) 2007 Elsevier Ltd. All rights reserved.