Current-induced spin polarization in nonmagnetic semiconductor junctions

TL;DR

This paper explains how electric fields and energy-dependent scattering in nonmagnetic semiconductors can induce spin polarization of current without requiring spin-orbit interactions, supported by analytic and numerical analysis.

Contribution

It introduces a mechanism for current-induced spin polarization in nonmagnetic semiconductors that does not rely on spin-orbit coupling, supported by theoretical and numerical evidence.

Findings

Spin polarization can be generated without spin-orbit interactions.

Analytic and numerical models support the proposed mechanism.

Explains recent experimental observations in GaAs junctions.

Abstract

Spontaneous spin polarization of the electrical current flowing through nonmagnetic semiconductor junctions can be generated by carrier scattering processes that are independent of the carrier spin. The two required elements for current-induced spin polarization are (1) the presence of built-in spatially-varying electric fields in the junction and (2) energy-dependent carrier scattering processes. Spin-orbit interactions are not required for this effect, thus it should occur in materials like silicon that lack significant spin-orbit interactions. Approximate analytic expressions as well as detailed numerical simulations of the time-dependent nonlinear spin transport in a GaAs junction strongly suggest that the recent experimental observation of current-induced spin polarization in this system [Y. Kato, R. C. Myers, A. C. Gossard, and D. D. Awschalom, Phys. Rev. Lett. 93, 176601 (2004)] may be explained by this effect.