Excitation of magnon spin photocurrents in antiferromagnetic insulators

TL;DR

This paper proposes a nonlinear effect where circularly polarized light induces a direct magnon spin current in antiferromagnetic insulators, conserving spin angular momentum and influenced by material geometry.

Contribution

It introduces a novel mechanism for generating magnon spin currents via circularly polarized light in antiferromagnetic insulators, including geometric effects in complex lattices.

Findings

Resonant second order light-matter interaction causes spin currents.

Spin current direction depends on light helicity.

Geometric contributions arise in complex lattice structures.

Abstract

In the circular photogalvanic effect, circularly polarized light can produce a direct electron photocurrent in metals and the direction of the current depends on the polarization. We suggest that an analogous nonlinear effect exists for antiferromagnetic insulators wherein the total spin of light and spin waves is conserved. In consequence, a spin angular momentum is expected to be transfered from photons to magnons so that a circularly polarized electromagnetic field will generate a direct magnon spin current. The direction of the current is determined by the helicity of the light. We show that this resonant effect appears as a second order light-matter interaction. We find also a geometric contribution to the spin photocurrent, which appears for materials with complex lattice structures and Dzyaloshinskii-Moriya interactions.