Bulk photospin effect: Calculation of electric spin susceptibility to second order in an electric field

TL;DR

This paper calculates the second-order electric spin susceptibility in Bloch electrons, revealing how linearly polarized fields can induce bulk spin polarization in non-magnetic materials, with implications for spintronics.

Contribution

It provides a second-order theoretical framework for electric spin susceptibility, including effects of interband coherence and spin multipole contributions, extending previous linear models.

Findings

Bulk spin polarization can be generated with linearly polarized fields.

Circular polarization may reduce heating effects.

Spin susceptibility includes dominant contributions from Fermi sea multipole moments.

Abstract

We compute the electric spin susceptibility of Bloch electrons with spin-orbit coupling to second order. We find that it is possible to generate a nonequilibrium spin polarization in the bulk of non-magnetic inversion-symmetric materials using linearly polarized electric fields, but the process depends on interband coherence and produces heating. It may be possible to avoid heating with circular polarization in certain scenarios. The standard Edelstein effect and spin orientation effects are recovered in appropriate limits within the formalism. Finally, the electric spin susceptibility of metals has contributions proportional to spin multipole moments of the Fermi sea that dominate the low frequency spin response.