Ultrafast recovery dynamics of dimer stripes in IrTe2

TL;DR

This study investigates the ultrafast dynamics of dimer formations in IrTe2, revealing rapid local dimer recovery within a few picoseconds after photoexcitation, contrasting with longer timescales for long-range order restoration.

Contribution

It provides the first direct measurement of the ultrafast local dimer dynamics in IrTe2 using time-resolved X-ray photoemission spectroscopy, highlighting the rapid local recovery process.

Findings

Dimer dissolution is driven by energy transfer from electrons to the lattice.

Local dimer distortions recover within a few picoseconds.

Long-range order takes tens of picoseconds to re-establish.

Abstract

The transition metal dichalcogenide IrTe2 displays a remarkable series of first-order phase transitions below room temperature, involving lattice displacements as large as 20 percents of the initial bond length. This is nowadays understood as the result of strong electron-phonon coupling leading to the formation of local multicentre dimers that arrange themselves into one-dimensional stripes. In this work, we study the out-of-equilibrium dynamics of these dimers and track the time evolution of their population following an infrared photoexcitation using free-electron lased-based time-resolved X-ray photoemission spectroscopy. First, we observe that the dissolution of dimers is driven by the transfer of energy from the electronic subsystem to the lattice subsystem, in agreement with previous studies. Second, we observe a surprisingly fast relaxation of the dimer population on the timescale of a few picoseconds. By comparing our results to published ultrafast electron diffraction and angle-resolved photoemission spectroscopy data, we reveal that the long-range order needs tens of picoseconds to recover, while the local dimer distortion recovers on a short timescale of a few picoseconds.