Robustness of the charge-ordered phases in IrTe$_2$ against photoexcitation

TL;DR

This study investigates the robustness of charge-ordered phases in IrTe$_2$ against photoexcitation, revealing that these phases are resistant to full phase transitions and only exhibit partial, transient changes upon femtosecond laser pulses.

Contribution

It demonstrates that the low-temperature charge-ordered phases in IrTe$_2$ are highly robust against photoinduced phase transitions, with only partial and transient spectral changes observed.

Findings

Photoinduced spectral changes occur within hundreds of femtoseconds.

The timescale for photoinducing changes increases with excitation density.

The low-temperature phase remains largely stable against photoexcitation.

Abstract

We present a time-resolved angle-resolved photoelectron spectroscopy study of IrTe$_2$, which undergoes two first-order structural and charge-ordered phase transitions on cooling below 270 K and below 180 K. The possibility of inducing a phase transition by photoexcitation with near-infrared femtosecond pulses is investigated in the charge-ordered phases. We observe changes of the spectral function occuring within a few hundreds of femtoseconds and persisting up to several picoseconds, which we interpret as a partial photoinduced phase transition (PIPT). The necessary time for photoinducing these spectral changes increases with increasing photoexcitation density and reaches timescales longer than the rise time of the transient electronic temperature. We conclude that the PIPT is driven by a transient increase of the lattice temperature following the energy transfer from the electrons. However, the photoinduced changes of the spectral function are small, which indicates that the low temperature phase is particularly robust against photoexcitation. We suggest that the system might be trapped in an out-of-equilibrium state, for which only a partial structural transition is achieved.