Light-induced Magnetic Phase Transition in van der Waals Antiferromagnets

TL;DR

This paper presents a theoretical framework and first-principles calculations demonstrating how light can induce a magnetic phase transition from antiferromagnetic to ferromagnetic states in 2D van der Waals materials, with implications for memory devices.

Contribution

The authors develop a general theory of light-induced magnetic phase transition in antiferromagnets based on bandgap differences and confirm it with first-principles calculations on 2D vdW antiferromagnets, including exciton effects.

Findings

Light excitation stabilizes ferromagnetic over antiferromagnetic states.

A critical photocarrier concentration triggers the phase transition.

The theory applies even considering strong exciton effects.

Abstract

Based on a simple tight-binding model, we propose a general theory of light-induced magnetic phase transition (MPT) in antiferromagnets based on the general conclusion that the bandgap of antiferromagnetic (AFM) phase is usually larger than that of ferromagnetic (FM) one in a given system. Light-induced electronic excitation prefers to stabilize the FM state over the AFM one, and once the critical photocarrier concentration ({\alpha}_c) is reached, an MPT from AFM phase to FM phase takes place. This theory has been confirmed by performing first-principles calculations on a series of two-dimensional (2D) van der Waals (vdW) antiferromagnets and a linear relationship between {\alpha}_c and the intrinsic material parameters is obtained. Importantly, our conclusion is still valid even considering the strong exciton effects during photoexcitation. Our general theory provides new ideas to realize reversible read-write operations for future memory devices.