Enhanced spin lifetimes in a two dimensional electron gas in a gate-controlled GaAs quantum well

TL;DR

This study demonstrates that by adjusting the gate voltage in a GaAs quantum well, the spin lifetime of a two-dimensional electron gas can be significantly increased, and the electron g-factor can be tuned.

Contribution

It provides a method to enhance spin lifetimes and control the g-factor in a 2D electron gas using gate voltage in a GaAs quantum well.

Findings

Spin decay time increased by a factor of 3 at optimal carrier density.

Carrier density tuning affects exciton and trion spectral weights.

Electron g-factor can be modulated via carrier density.

Abstract

Exciton, trion and electron spin dynamics in a 20 nm wide modulation-doped GaAs single quantum well are investigated using resonant ultrafast two-color Kerr rotation spectroscopy. Excitons and trions are selectively detected by resonant probe pulses while their relative spectral weight is controlled by adjusting the gate voltage which tunes the carrier density. Tuning the carrier density markedly influences the spin decay time of the two dimensional electron gas. The spin decay time can be enhanced by a factor of 3 at an intermediate carrier concentration in the quantum well, where excitons and trions coexist in the system. In addition, we explore the capability to tune the g-factor of the electron gas via the carrier density.