Ultrafast magneto-lattice dynamics in two-dimensional CrSBr driven by terahertz excitation

TL;DR

This paper explores ultrafast magneto-lattice dynamics in monolayer CrSBr driven by terahertz excitation, revealing rapid demagnetization processes and the role of specific phonon modes in spin and charge interactions.

Contribution

It uncovers the detailed two-stage demagnetization process and identifies the specific phonon vibration modes influencing electron relaxation and spin dynamics in 2D CrSBr.

Findings

Demagnetization occurs within 20 fs driven by electron transfer.

B3g1 phonon mode relaxes in 83 fs, faster than previously thought.

Coherent phonons significantly influence spin changes, up to 215%.

Abstract

Terahertz (THz) lasers provide a new research perspective for spin electronics applications due to their sub-picosecond time resolution and non-thermal ultrafast demagnetization, but the interaction between spin, charge and lattice dynamics remains unclear. This study investigates photoinduced ultrafast demagnetization in monolayer CrSBr, a two-dimensional material with strong spin-orbit and spin-lattice coupling, and resolves its demagnetization process. Two key stages are identified: the first, occurring within 20 fs, is characterized by rapid electron-driven demagnetization, where charge transfer and THz laser are strongly coupled. In the second stage, light-induced lattice vibrations coupled to spin dynamics lead to significant spin changes, with electron-phonon coupling playing a key role. Importantly, the role of various phonon vibration modes in the electron relaxation process was clearly determined, pointing out that the electronic relaxation of the B3g1 phonon vibration mode occurs within 83 fs, which is less than the commonly believed 100 fs. Moreover, the influence of this coherent phonon on the demagnetization change is as high as 215 %. These insights into multiscale magneto-structural coupling advance the understanding of nonequilibrium spin dynamics and provide guidelines for the design of light-controlled quantum devices, particularly in layered heterostructures for spintronics and quantum information technologies.