Spin polarization control by electric field gradients

TL;DR

This paper demonstrates that inhomogeneous electric field gradients significantly influence spin diffusion length, revealing a new electrical control mechanism for spin transport in semiconductor spintronics.

Contribution

It introduces a generalized drift-diffusion model incorporating electric field gradients, validated by numerical Boltzmann transport calculations, highlighting a novel electrical effect on spin transport.

Findings

Spin diffusion length depends on electric field gradients.

Electric field gradients can enhance or suppress spin transport.

A new drift-diffusion equation accounts for these effects.

Abstract

We show that the propagation of spin polarized carriers may be dramatically affected by {\em inhomogeneous} electric fields. Surprisingly, the spin diffusion length is found to strongly depend on the sign and magnitude of electric field \emph{gradients}, in addition to the previously reported dependence on the sign and magnitude of the electric field [Yu & Flatt\'e, Phys. Rev. B {\bf 66}, 201202(R) 2002; {\em ibid.} {\bf 66}, 235302 (2002)]. This indicates that purely electrical effects may play a crucial role in spin polarized injection, transport and detection in semiconductor spintronics. A generalized drift-diffusion equation that describes our findings is derived and verified by numerical calculations using the Boltzmann transport equation.