Dynamic of Spin Triplet and Singlet Trions in a GaAs Quantum Well

Abstract

In this paper we discuss the dynamics of the spin-triplet and spin-singlet states of the negatively charged exciton in a 300 A quantum well (QW) under a perpendicular magnetic field. The singlet spin state shows similar behaviour to that already observed for the trion at 0 T. However, the triplet state (which is supposed to be optically inactive) shows a very long decay time at low electron concentrations which shortens upon adding carriers to the well. For this reason we have modeled the perturbation to the trion triplet wavefunction caused by the excess electrons, and found an enhancement of its oscillator strength with electron density, which follows a cubic power law. The same power law is also found for the experimental variation of the triplet decay rate (proportional to the trion oscillator strength). This justifies the fact that the trion triplet state, in presence of an excess electron concentration, can have a finite oscillator strength.