# Asymmetric Spin Canting and Demagnetization Dynamics Driven by Laser Fields in Two-Dimensional Altermagnets

## TL;DR

This paper explores how laser pulses can control magnetization in a 2D altermagnet, creating a new state with net magnetization and tunable spin dynamics.

## Contribution

The study reveals asymmetric demagnetization and spin canting in 2D altermagnets driven by laser fields, a previously unexplored phenomenon.

## Key findings

- Laser pulses induce a photoinduced ferrimagnetic state with 0.3 μB net magnetization per unit cell in Fe2WTe4.
- Spin canting angles differ between Fe sublattices due to non-collinear spin dynamics.
- Spin dynamics are tunable via the in-plane polarization angle of the laser field.

## Abstract

Laser-induced ultrafast magnetization dynamics have been
well established
in conventional magnets but remain unexplored in altermagnets (AMs).
Using real-time time-dependent density functional theory (rt-TDDFT),
we demonstrate that laser pulses can drive asymmetric demagnetization
dynamics between the two Fe sublattices in the two-dimensional (2D)
semiconducting AM, Fe2WTe4, leading to a photoinduced
ferrimagnetic state with a net magnetization of approximately 0.3
μB per unit cell. This metastable magnetization originates
from the momentum-dependent spin-splitting characteristic of d-wave AMs, which gives rise to an anisotropic optical intersite
spin transfer effect (OISTR). Furthermore, the asymmetric demagnetization
is accompanied by non-collinear spin dynamics, resulting in distinct
spin canting angles for two Fe sublattices. Importantly, these spin
dynamics are tunable by the in-plane polarization angle of the laser
field. Our findings provide microscopic insight into the ultrafast
control of magnetization in 2D AMs and open new avenues for light-driven
manipulation of spin textures in AM systems.