Break of symmetry at the surface of IrTe$_2$ upon phase transition measured by X-ray photoelectron diffraction

TL;DR

This study uses X-ray photoelectron diffraction to investigate atomic surface changes in IrTe$_2$ during phase transitions, revealing symmetry breaking and surface reconstruction involving Ir dimers.

Contribution

It provides direct experimental evidence of surface atomic rearrangements and symmetry breaking in IrTe$_2$ during phase transitions, using XPD techniques.

Findings

Identified symmetry breaking from trigonal to monoclinic surface structure.

Confirmed the (5×1) surface reconstruction involving dimer stacking.

Demonstrated surface atomic environment changes across phase transition.

Abstract

IrTe$_2$ undergoes a series of charge-ordered phase transitions below room temperature that are characterized by the formation of stripes of Ir dimers of different periodicities. Full hemispherical X-ray photoelectron diffraction (XPD) experiments have been performed to investigate the atomic position changes undergone near the surface of $1T-$IrTe$_2$ in the first-order phase transition, from the $(1\times1)$ phase to the $(5\times1)$ phase. Comparison between experiment and simulation allows us to identify the consequence of the dimerization on the Ir atoms local environment. We report that XPD permits to unveil the break of symmetry of IrTe$_2$ trigonal to a monoclonic unit cell and confirm the occurence of the $(5\times1)$ reconstruction within the first few layers below the surface with a staircase-like stacking of dimers.