Anomalous magnetic suppression of spin relaxation in a two-dimensional electron gas in a GaAs/AlGaAs quantum well

TL;DR

This paper investigates the unusual magnetic field effects on spin relaxation in a high-mobility 2D electron gas within a GaAs/AlGaAs quantum well, revealing a transition from quadratic to linear dependence and oscillatory behavior linked to electron gyration and density of states.

Contribution

It uncovers the anomalous magnetic suppression of spin relaxation and connects it to classical to Bohm diffusion transition in a 2D electron gas, a novel insight into spin dynamics.

Findings

Spin relaxation time first increases quadratically then linearly with magnetic field.

Oscillations in spin relaxation correspond to Landau level filling factors.

Suppression of spin relaxation due to electron gyration effects.

Abstract

We study the spin dynamics in a high-mobility two-dimensional electron gas confined in a GaAs/AlGaAs quantum well. An unusual magnetic field dependence of the spin relaxation is found: as the magnetic field becomes stronger, the spin relaxation time first increases quadratically but then changes to a linear dependence, before it eventually becomes oscillatory, whereby the longitudinal and transverse times reach maximal values at even and odd filling Landau level factors, respectively. We show that the suppression of spin relaxation is due to the effect of electron gyration on the spin-orbit field, while the oscillations correspond to oscillations of the density of states appearing at low temperatures and high magnetic fields. The transition from quadratic to linear dependence can be related to a transition from classical to Bohm diffusion and reflects an anomalous behavior of the two-dimensional electron gas analogous to that observed in magnetized plasmas.