Laser-induced torques in metallic antiferromagnets

TL;DR

This paper investigates laser-induced torques in the antiferromagnet Mn$_2$Au, revealing that linearly polarized light can induce significant torques comparable to ferromagnets and introducing a new Wannier interpolation method for spin-orbit interactions.

Contribution

It demonstrates laser-induced torques in Mn$_2$Au$ that do not require circular polarization and introduces WISOI, a new Wannier interpolation technique for spin-orbit interactions.

Findings

Linearly polarized light induces torques in Mn$_2$Au.

Laser-induced torques are comparable to ferromagnets at optical frequencies.

Spin-orbit torques dominate at THz frequencies for experimental field strengths.

Abstract

We study the laser-induced torques in the antiferromagnet (AFM) Mn$_2$Au. We find that even linearly polarized light may induce laser-induced torques in Mn$_2$Au, i.e., the light does not have to be circularly polarized. The laser-induced torques in Mn$_2$Au are comparable in magnitude to those in the ferromagnets Fe, Co and FePt at optical frequencies. We also compute the laser-induced torques at terahertz (THz) frequencies and compare them to the spin-orbit torques (SOTs) excited by THz laser-pulses. We find the SOTs to be dominant at THz frequencies for the laser-field strengths used in experiments. Additionally, we show that the matrix elements of the spin-orbit interaction (SOI) can be used to add SOI only during the Wannier interpolation, which we call Wannier interpolation of SOI (WISOI). This technique allows us to perform the Wannier interpolation conveniently for many magnetization directions from a single set of Wannier functions.