Nonlinear photomagnetization in insulators

TL;DR

This paper investigates how oscillating electric fields can induce static magnetization in insulators through nonlinear effects, revealing symmetry constraints and computationally demonstrating significant potential for photomagnetization.

Contribution

It identifies symmetry conditions for nonlinear photomagnetization and computes the second-order electric spin susceptibility in various semiconductors using density functional theory.

Findings

All 32 point groups allow spin polarization with circular polarization.

29 point groups allow spin polarization with linear polarization.

Nonlinear photomagnetization can be comparable to ferromagnets.

Abstract

Nonlinear photomagnetization is a process by which an oscillating electric field induces a static magnetization. We show that all 32 crystallographic point groups admit such spin polarization using circularly polarized electric fields to second order (as in the usual spin orientation or inverse Faraday effect) but only 29 points groups admit spin polarization using linearly polarized electric fields to second order. The excluded point groups are the highly symmetric $m$-3$m$, -$43m$ and 432. Using density functional theory we compute the spectrum of the second-order electric spin susceptibility of prototypical semiconductors Te, Se, SnS$_2$, GaAs, InSb and Si which corresponds to nonmagnetic materials with and without inversion symmetry. We show that nonlinear photomagnetization can be comparable to those of naturally occurring ferromagnets.