Manipulation of ferromagnetism with a light-driven nonlinear Edelstein-Zeeman field

TL;DR

This paper demonstrates ultrafast, non-thermal optical control of ferromagnetism in a centrosymmetric material via a nonlinear Edelstein effect, enabling magnetic manipulation through light in a way previously thought symmetry-forbidden.

Contribution

It introduces a novel nonlinear optical mechanism to control magnetism in centrosymmetric materials using a resonant nonlinear Edelstein effect, supported by experimental THz emission spectroscopy.

Findings

Direct observation of magnetic dipole radiation from optically driven magnetization dynamics.

Quantitative agreement with a mean-field model of a weakly anisotropic Heisenberg ferromagnet.

Establishment of a general nonequilibrium method for optical control of magnetism in centrosymmetric materials.

Abstract

Optical control of magnetization is often symmetry-forbidden because electric fields and magnetization transform differently under inversion and time-reversal. However, through even-order nonlinear response, optical excitation can generate a nonequilibrium magnetic density (the nonlinear Edelstein effect) that acts as an internal Edelstein-Zeeman field coupling to slower magnetic degrees of freedom. Here we demonstrate non-thermal, ultrafast optical control of ferromagnetism in the centrosymmetric van der Waals semiconductor Cr$_2$Ge$_2$Te$_6$ via a resonant nonlinear Edelstein effect. Using time-domain THz emission spectroscopy under near-infrared excitation, we directly observe magnetic dipole radiation arising from optically driven magnetization dynamics. The polarization, fluence, and temperature dependences of the THz emission are quantitatively captured by a mean-field description of a weakly anisotropic Heisenberg ferromagnet subject to an Edelstein-Zeeman field. Our results establish a general nonequilibrium route to optical control of magnetism in centrosymmetric materials.