Ab Initio Theory of Coherent Laser-Induced Magnetization in Metals

TL;DR

This paper develops the first ab initio theory for laser-induced magnetization in metals, revealing material-specific behaviors and guiding all-optical magnetic switching techniques.

Contribution

It introduces a materials-specific ab initio framework for understanding laser-induced magnetization, including effects of absorption and frequency dependence.

Findings

Induced magnetization varies strongly with material and frequency.

Spin and orbital magnetizations behave differently under laser excitation.

Guidelines for all-optical helicity-dependent switching are provided.

Abstract

We present the first materials specific ab initio theory of the magnetization induced by circularly polarized laser light in metals. Our calculations are based on non-linear density matrix theory and include the effect of absorption. We show that the induced magnetization, commonly referred to as inverse Faraday effect, is strongly materials and frequency dependent, and demonstrate the existence of both spin and orbital induced magnetizations which exhibit a surprisingly different behavior. We show that for nonmagnetic metals (as Cu, Au, Pd, Pt) and antiferromagnetic metals the induced magnetization is antisymmetric in the light's helicity, whereas for ferromagnetic metals (Fe, Co, Ni, FePt) the imparted magnetization is only asymmetric in the helicity. We compute effective optomagnetic fields that correspond to the induced magnetizations and provide guidelines for achieving all-optical helicity-dependent switching.