Ambipolar spin-spin coupling in p$^+$-GaAs

TL;DR

This paper introduces a new spin-spin coupling mechanism in semiconductors caused by ambipolar electric fields, demonstrated in p$^+$-GaAs, which affects local spin polarization without altering overall charge transport.

Contribution

It reports the discovery of a novel ambipolar spin-spin coupling mechanism during spin-polarized electron transport in semiconductors.

Findings

Coupling reduces local spin polarization with increased excitation power

Mechanism is distinct from Coulomb spin drag and does not affect charge diffusion

Experimental evidence obtained via polarized microluminescence in p$^+$-GaAs

Abstract

A novel spin-spin coupling mechanism that occurs during the transport of spin-polarized minority electrons in semiconductors is described. Unlike the Coulomb spin drag, this coupling arises from the ambipolar electric field which is created by the differential movement of the photoelectrons and the photoholes. Like the Coulomb spin drag, it is a pure spin coupling that does not affect charge diffusion. Experimentally, the coupling is studied in $p^+$ GaAs using polarized microluminescence. The coupling manifests itself as an excitation power dependent reduction in the spin polarization at the excitation spot \textit{without} any change of the spatially averaged spin polarization.