Electron spin relaxation as tracer of excitons in a two-dimensional electron-hole plasma inside a (110)-GaAs quantum well

摘要

We show that a fast electron spin relaxation time in (110)-oriented GaAs/AlGaAs quantum wells is governed by the presence of excitons at low temperatures and intermediate excitation densities. The electron loses its spin orientation within an exciton due to the long-range part of the exciton anisotropic spin exchange interaction and unveils excitonic signatures within the many particle electron-hole system. The temperature-dependent time- and polarization-resolved photoluminescence measurements span five decades of carrier density, comprise the transition from localized excitons over quasi-free excitons to an electron-hole plasma, and reveal strong excitonic signatures even at relatively high densities and temperatures.