Electrical Control of Hole Spin Relaxation in Charge TunableInAs/GaAsQuantum Dots

Abstract

We report on optical orientation of singly charged excitons (trions) in charge-tunable self-assembled $\mathrm{InAs}/\mathrm{GaAs}$ quantum dots. When the charge varies from 0 to $-2$, the trion photoluminescence of a single quantum dot shows up and under quasiresonant excitation gets progressively polarized from zero to $\sim 100\%$. This behavior is interpreted as the electric control of the trion thermalization process, which subsequently acts on the hole-spin relaxation driven in nanosecond time scale by the anisotropic electron-hole exchange. This is supported by the excitation spectroscopy and time-resolved measurements of a quantum dot ensemble.