Dynamic short-range correlation in photoinduced disorder phase transitions

TL;DR

This paper uses real-time simulations to explore how photoinduced phase transitions in IrTe2 involve both coherent and disordered atomic displacements, revealing local correlations in dimer dissociation.

Contribution

It uncovers the existence of local correlation patterns in disordered phase transitions, distinguishing between coherent and disordered atomic displacements in photoinduced transitions.

Findings

Disordered phase transition involves local correlation between dimers.

Dimers in the same vertical group dissociate collectively.

Neighboring groups of dimers tend to have anti-correlated dissociation behavior.

Abstract

Ultrafast photoexcitation can induce a nonequilibrium dynamic with electron-lattice interaction, offering an effective way to study photoinduced phase transitions (PIPTs) in solids. The issue that atomic displacements after photoexcitation belong to coherent change or disordered process, has become a controversy in the PIPT community. Using real-time time-dependent density functional theory (rt-TDDFT) simulations, we obtain both the coherent and the disordered PIPTs (dimer dissociation) in IrTe2 with the different electronic occupations. More importantly, we found that in the disordered phase transition, there exists a local correlation between different dimers regarding their dissociation status. One can define vertical groups across the layers. The dimers in the same group will dissociate in a correlated fashion: they either all dissociate, or all not dissociate. On the other hand, the dimers in neighboring groups will have an anti-correlation: if the dimers in one group dissociate, the dimers in the neighboring group tend not to be dissociated, and vice versus.