Ultrafast cooling and heating scenarios for the laser induced phase transition in CuO

TL;DR

This study uses atomistic spin dynamics simulations to explore ultrafast laser-induced phase transitions in CuO, revealing distinct cooling and heating pathways on picosecond timescales due to different excitation mechanisms.

Contribution

It demonstrates, through simulations, how phonon-assisted multimagnon absorption and photodoping induce ultrafast magnetic phase transitions in CuO with distinct thermal dynamics.

Findings

Photodoping causes ultrafast spin system cooling via a magnetocaloric effect.

Phonon-assisted multimagnon excitation leads to rapid heating and phase change.

Both mechanisms enable phase transition on picosecond timescales.

Abstract

The multiferroic compound CuO exhibits low temperature magnetic properties similar to antiferromagnetic iron oxides, while the electronic properties have much more in common with the high $T_c$ cuprate superconductors. This suggests novel possibilities for the ultrafast optical excitation of magnetism. On the basis on atomistic spin dynamics simulations, we study the effect of phonon-assisted multimagnon absorption and photodoping on the spin dynamics in the vicinity of the first-order phase transition from collinear to spin-spiral magnetic order. Similar as in recent experiments, we find that for both excitations the phase transition can proceed on the picosecond timescale. Interestingly, however, these excitation mechanisms display very distinct dynamics. Following photodoping, the spin system first cools down on sub-ps timescales, which we explain as an ultrafast magnetocaloric effect. Opposed to this, following phonon-assisted multimagnon excitation the spin systems rapidly heats up and subsequently evolves to the noncollinear phase even under the influence of isotropic exchange interactions alone.