Tunable spin polarization in III-V quantum wells with a ferromagnetic barrier

TL;DR

This study demonstrates tunable spin polarization in III-V quantum wells with a ferromagnetic barrier, achieved through epitaxial growth and electrical gating, revealing a new method for controlling spin states without current injection.

Contribution

It introduces a novel approach to control spin polarization in quantum wells via wave function overlap and electrical bias, without relying on electrical or optical spin injection.

Findings

Spin polarization can be tuned from -0.4% to 6.3% at 5 K.

Polarization is mediated by wave function overlap with Mn-ions.

Polarization occurs with negligible current flow, independent of initial spin orientation.

Abstract

We demonstrate the epitaxial growth of optical-quality electrically-gated III-V ferromagnetic quantum structures. Photoluminescence spectroscopy reveals that initially unpolarized photoexcited holes in a GaAs quantum well become spin-polarized opposite to the magnetization of an adjacent digital ferromagnetic layer in the AlGaAs barrier. A vertical bias is used to tune the spin polarization from -0.4 to 6.3 percent at T = 5 K and B = 1 kG during which the luminescence becomes quenched, indicating that the polarization is mediated by wave function overlap between heavy holes in the quantum well and Mn-ions in the barrier. Polarization is observed under negligible current flow and is insensitive to the initial spin orientation of the carriers, differentiating the effect from both electrical and optical spin injection.