Electrical control of spin relaxation anisotropy during drift transport in a two-dimensional electron gas

TL;DR

This study demonstrates electrical control of spin relaxation anisotropy during drift transport in a two-dimensional electron gas, revealing direction-dependent spin lifetimes influenced by in-plane electric fields and gate voltages.

Contribution

It provides the first demonstration of electrical control of spin relaxation anisotropy in a multi-subband 2DEG system during drift transport, highlighting effects beyond existing models.

Findings

Strong anisotropy of spin relaxation times with transport direction.

Gate-dependent spin lifetime along the [1-10] direction.

Longer spin lifetime observed along [1-10] compared to [110].

Abstract

Spin relaxation was studied in a two-dimensional electron gas confined in a wide GaAs quantum well. Recently, the control of the spin relaxation anisotropy by diffusive motion was first shown in D. Iizasa et al., arXiv:2006.08253 (2020). Here, we demonstrate electrical control by drift transport in a system with two-subbands occupied. The combined effect of in-plane and gate voltages was investigated using time-resolved Kerr rotation. The measured relaxation time present strong anisotropy with respect to the transport direction. For an in-plane accelerating electric field along $\left[110\right]$, the lifetime was strongly suppressed irrespective of the applied gate voltage. Remarkably, for transport along $\left[1\bar{1}0\right]$, the data shows spin lifetime that was gate-dependent and longer than in the $\left[110\right]$ direction regardless of the in-plane voltage. In agreement, independent results of anisotropic spin precession frequencies are also presented. Nevertheless, the long spin lifetime, strong anisotropy and drift response seen in the data are beyond the existing models for spin drift and diffusion.