Terahertz field-induced metastable magnetization near criticality in FePS3

TL;DR

This paper demonstrates that intense terahertz pulses can induce a long-lived metastable magnetization in FePS3, especially near the critical temperature, revealing a non-thermal pathway to manipulate magnetic states in layered quantum materials.

Contribution

It introduces a novel method of using terahertz light to create metastable magnetic states with millisecond lifetimes near criticality in FePS3, combining experimental and computational insights.

Findings

Metastable magnetization persists over 2.5 milliseconds.

Metastability is enhanced near the antiferromagnetic transition temperature.

Phonon mode displacement modulates exchange couplings, favoring finite magnetization.

Abstract

Controlling the functional properties of quantum materials with light has emerged as a frontier of condensed-matter physics, leading to the discovery of various light-induced phases of matter, such as superconductivity, ferroelectricity, magnetism and charge density waves. However, in most cases, the photoinduced phases return to equilibrium on ultrafast timescales after the light is turned off, limiting their practical applications. Here we use intense terahertz pulses to induce a metastable magnetization with a remarkably long lifetime of more than 2.5 milliseconds in the van der Waals antiferromagnet FePS3. The metastable state becomes increasingly robust as the temperature approaches the antiferromagnetic transition point, suggesting that critical order parameter fluctuations play an important part in facilitating the extended lifetime. By combining first-principles calculations with classical Monte Carlo and spin dynamics simulations, we find that the displacement of a specific phonon mode modulates the exchange couplings in a manner that favours a ground state with finite magnetization near the N\'eel temperature. This analysis also clarifies how the critical fluctuations of the dominant antiferromagnetic order can amplify both the magnitude and the lifetime of the new magnetic state. Our discovery demonstrates the efficient manipulation of the magnetic ground state in layered magnets through non-thermal pathways using terahertz light and establishes regions near critical points with enhanced order parameter fluctuations as promising areas to search for metastable hidden quantum states.