Ultrafast laser-induced spin-lattice dynamics in the van der Waals antiferromagnet CoPS3

TL;DR

This study investigates how femtosecond laser pulses induce ultrafast spin and lattice dynamics in CoPS3, revealing a coupling mechanism between electronic excitation, orbital momentum change, and coherent phonon generation.

Contribution

It demonstrates the direct laser-driven manipulation of spin-lattice interactions in CoPS3 through resonant electronic excitation and coherent phonon generation.

Findings

Femtosecond laser pulses melt antiferromagnetic order in CoPS3.

Resonant excitation induces a coherent phonon mode at 4.7 THz.

Orbital momentum changes drive ionic motion and spin-lattice coupling.

Abstract

CoPS3 stands out in the family of the van der Waals antiferromagnets XPS3 (X=Mn, Ni, Fe, Co) due to the unquenched orbital momentum of the magnetic Co2+ ions which is known to facilitate the coupling of spins to both electromagnetic waves and lattice vibrations. Here, using a time-resolved magneto-optical pump-probe technique we experimentally study the ultrafast laser-induced dynamics of mutually correlated spins and lattice. It is shown that a femtosecond laser pulse acts as an ultrafast heater and thus results in the melting of the antiferromagnetic order. At the same time, the resonant pumping of the 4T1g - 4T2g electronic transition in Co2+ ions effectively changes their orbital momentum, giving rise to a mechanical force that moves the ions in the direction parallel to the orientation of their spins, thus generating a coherent Bg phonon mode at the frequency of about 4.7 THz.