Ultrafast coherent THz lattice dynamics coupled to spins in a van der Waals antiferromagnetic flake

TL;DR

This study demonstrates ultrafast coherent THz lattice dynamics coupled to spins in a van der Waals antiferromagnetic material, revealing a pathway for femtosecond control of magneto-crystalline properties.

Contribution

It uncovers the direct link between photo-induced lattice modes and magnetic order in FePS3, showing potential for ultrafast magnetic manipulation.

Findings

Photo-induced phonon generated by femtosecond laser pulses

Phonon amplitude decreases with temperature and vanishes at Néel temperature

Lattice mode is connected to long-range magnetic order

Abstract

A coherent THz optical lattice mode is triggered by femtosecond laser pulses in the antiferromagnetic van der Waals semiconductor FePS$_3$. The 380 nm thick exfoliated flake was placed on a substrate and laser-driven lattice and spin dynamics were investigated as a function of the excitation photon energy and sample temperature. The pump-probe spectroscopic measurements reveal that the photo-induced phonon is generated by a displacive mechanism. The amplitude of the phononic signal decreases as the sample is heated up to the N\'eel temperature and vanishes as the phase transition to the paramagnetic phase occurs. This evidence confirms that the excited lattice mode is intimately connected to the long-range magnetic order. Therefore our work discloses a pathway towards a femtosecond coherent manipulation of the magneto-crystalline anisotropy in a van der Waals antiferromagnet. In fact, it is reported that by applying a magnetic field the induced phonon mode hybridizes via the Kittel-mechanism with zone-centre magnons.