Ultrafast laser-induced spin–lattice dynamics in the van der Waals antiferromagnet CoPS 3
CoPS 3 stands out in the family of the van der Waals antiferromagnets XPS 3 (X = Mn, Ni, Fe, and Co) due to the unquenched orbital momentum of the magnetic Co 2+ 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 4 T 1g → 4 T 2g electronic transition in Co 2+ 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 B g phonon mode at the frequency of about 4.7 THz.