Spin dynamics of electrons and holes in InGaAs/GaAs quantum wells at milliKelvin temperatures

TL;DR

This study investigates electron and hole spin dynamics in n-doped InGaAs/GaAs quantum wells at milliKelvin temperatures, revealing localization effects and long-lived spin coherence with implications for quantum information applications.

Contribution

It provides experimental data on spin relaxation times at ultra-low temperatures and discusses mechanisms of spin coherence generation and relaxation in quantum wells.

Findings

Electron spin relaxation saturates at 45 ns below 4.5 K.

Hole spin relaxation saturates at 2 ns below 2.3 K.

Carrier localization influences spin relaxation times.

Abstract

The carrier spin dynamics in a n-doped (In,Ga)As/GaAs quantum well has been studied by time-resolved Faraday rotation and ellipticity techniques in the temperature range down to 430 milliKelvin. These techniques give data with very different spectral dependencies, from which nonetheless consistent information on the spin dynamics can be obtained, in agreement with theoretical predictions. The mechanisms of long-lived spin coherence generation are discussed for the cases of trion and exciton resonant excitation. We demonstrate that carrier localization leads to a saturation of spin relaxation times at 45 ns for electrons below 4.5 K and at 2 ns for holes below 2.3 K. The underlying spin relaxation mechanisms are discussed.