Pressure dependence of the local structure of iridium ditelluride across the structural phase transition

Abstract

The local structure of ${\mathrm{IrTe}}_{2}$ has been studied by iridium ${L}_{3}$-edge x-ray absorption spectroscopy (XAS) measurements as a function of pressure, performed at two temperatures (100 and 295 K) across the structural phase transition at $\ensuremath{\sim}270$ K. Extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectra show pressure-dependent anomalies, suggesting phase transitions that are characterized by different local atomic displacements. The high-temperature phase of ${\mathrm{IrTe}}_{2}$ (trigonal at 295 K) reveals a clear anomaly in the Ir-Te correlations at $\ensuremath{\sim}4$ GPa, while the low-temperature phase (at 100 K) shows a smaller change at $\ensuremath{\sim}6$ GPa, likely to be associated with transitions in lower-symmetry phases. XANES spectra, measuring higher-order atomic correlations, also show nonlinear pressure dependence in the local geometry at the anomalous pressures. These nonlinear changes suggest that ${\mathrm{IrTe}}_{2}$ goes through lower local symmetry phases with increasing pressure.