First-order kinetics bottleneck during photoinduced ultrafast insulator-metal transition in 3D orbitally-driven Peierls insulator CuIr${}_2$S${}_4$

Abstract

Ultrafast dynamics across the photoinduced three-dimensional Peierls-like insulator-metal (IM) transition in CuIr${}_2$S${}_4$ was investigated by means of the all-optical ultrafast multi-pulse time-resolved spectroscopy. The structural coherence of the low-$T$ broken symmetry state is strongly suppressed on a sub-picosecond timescale above a threshold excitation fluence of $F_{\mathrm{c}}\approx 3$ mJ/cm${}^2$ (at 1.55-eV photon energy) resulting in a structurally inhomogeneous transient state which persists for several-tens of picoseconds before reverting to the original low-$T$ state. The electronic order shows a transient gap filling at a significantly lower fluence threshold of $\sim 0.6$~mJ/cm${}^2$. The data suggest that the photoinduced-transition structural dynamics to the high-$T$ metallic phase is governed by first-order-transition nucleation kinetics that prevents the complete structural transition into the high-$T$ phase even at excitation fluences significantly larger than $F_{\mathrm{c}}$. In contrast, the dynamically-decoupled electronic order is suppressed rather independently due to a photoinduced Mott transition.

By mistake resubmitted as 2104.03698