Controlling the anisotropy of a van der Waals antiferromagnet with light

TL;DR

This paper demonstrates all-optical control of magnetic anisotropy in a 2D van der Waals antiferromagnet, NiPS3, by tuning light to orbital resonances, enabling manipulation of magnetic order via ultrashort pulses.

Contribution

It introduces a novel method to control magnetic anisotropy in 2D antiferromagnets using resonant light pulses, revealing a universal approach for low-dimensional magnetic manipulation.

Findings

Selective activation of a magnon mode via resonant light.

Polarization-dependent control confirms anisotropy manipulation.

Orbital resonance pumping as a universal magnetic control route.

Abstract

Magnetic van der Waals materials provide an ideal playground for exploring the fundamentals of low-dimensional magnetism and open new opportunities for ultrathin spin processing devices. The Mermin-Wagner theorem dictates that as in reduced dimensions isotropic spin interactions cannot retain long-range correlations; the order is stabilized by magnetic anisotropy. Here, using ultrashort pulses of light, we demonstrate all-optical control of magnetic anisotropy in the two-dimensional van der Waals antiferromagnet NiPS$_3$. Tuning the photon energy in resonance with an orbital transition between crystal-field split levels of the nickel ions, we demonstrate the selective activation of a sub-THz two-dimensional magnon mode. The pump polarization control of the magnon amplitude confirms that the activation is governed by the instantaneous magnetic anisotropy axis emergent in response to photoexcitation of orbital states with a lowered symmetry. Our results establish pumping of orbital resonances as a universal route for manipulating magnetic order in low-dimensional (anti)ferromagnets.