First-order kinetics bottleneck during photoinduced ultrafast insulator–metal transition in 3D orbitally-driven Peierls insulator CuIr2S4

M Naseska,D Svetin,V V Kabanov,I Vaskivskyi,Y Vaskivskyi,T Mertelj,P Sutar,D Vengust,D Mihailovic

doi:10.1088/1367-2630/abf86d

Abstract

The spinel-structure CuIr2S4 compound displays a rather unusual orbitally-driven three-dimensional Peierls-like insulator–metal transition. The low-T symmetry-broken insulating state is especially interesting due to the existence of a metastable irradiation-induced disordered weakly conducting state. Here we study intense femtosecond optical pulse irradiation effects by means of the all-optical ultrafast multi-pulse time-resolved spectroscopy. We show that the structural coherence of the low-T broken symmetry state is strongly suppressed on a sub-picosecond timescale above a threshold excitation fluence resulting in a structurally inhomogeneous transient state which persists for several-tens of picoseconds before reverting to the low-T disordered weakly conducting state. The electronic order shows a transient gap filling at a significantly lower fluence threshold. The data suggest that the photoinduced-transition dynamics to the high-T metallic phase is governed by first-order-transition nucleation kinetics that prevents the complete ultrafast structural transition even when the absorbed energy significantly exceeds the equilibrium enthalpy difference to the high-T metallic phase.

Highlights

Kinetics of first order phase transitions are important both from the point of view of applications as well as fundamental science
We show that the structural coherence of the low-T broken symmetry state is strongly suppressed on a sub-picosecond timescale above a threshold excitation fluence resulting in a structurally inhomogeneous transient state which persists for several-tens of picoseconds before reverting to the low-T disordered weakly conducting state
Since the exact optical dered weakly conducting (DWC)-phase-creation conditions are not known we measured the low-T DC photoconductivity (see Supplemental Material (SM)45) and found, as suggested previously,[40] that even at the lowest feasible excitation fluences, F ∼100 μJ/cm[2], the threshold dose is exceeded on a timescale faster than a single transient reflectivity scan acquisition time of ∼100 s

Summary

Introduction

Kinetics of first order phase transitions are important both from the point of view of applications as well as fundamental science. Ultrafast first-order insulator-metal (IM) phase transitions could be instrumental for ultrafast sensor and nonvolatile memory applications. Their ultrafast kinetics attracted a great deal of attention[3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26] with strong focus on VO23,5,7,8,12,13,15,19,24–26, V2O314,18,21,23 and 1T -TaS26,11,16,20,22. There are still open questions how the inherent first-order meta-stability manifests itself when phases with concurrent electronic and lattice orders are driven across the first-order phase boundary on ultrafast time scales

Methods

Results

Conclusion