Structural phase transition in IrTe$_2$: A combined study of optical spectroscopy and band structure calculations

TL;DR

This study investigates the electronic and structural changes in IrTe$_2$ across a phase transition using optical spectroscopy and band structure calculations, revealing a crystal field-driven transition rather than a density wave instability.

Contribution

It combines optical spectroscopy with density functional calculations to elucidate the origin of the structural phase transition in IrTe$_2$, highlighting the role of crystal field effects.

Findings

Significant band structure reconstruction below 280 K

Reduction in conducting carriers during transition

Transition driven by crystal field effects, not density wave instability

Abstract

Ir$_{1-x}$Pt$_x$Te$_2$ is an interesting system showing competing phenomenon between structural instability and superconductivity. Due to the large atomic numbers of Ir and Te, the spin-orbital coupling is expected to be strong in the system which may lead to nonconventional superconductivity. We grew single crystal samples of this system and investigated their electronic properties. In particular, we performed optical spectroscopic measurements, in combination with density function calculations, on the undoped compound IrTe$_2$ in an effort to elucidate the origin of the structural phase transition at 280 K. The measurement revealed a dramatic reconstruction of band structure and a significant reduction of conducting carriers below the phase transition. We elaborate that the transition is not driven by the density wave type instability but caused by the crystal field effect which further splits/separates the energy levels of Te (p$_x$, p$_y$) and Te p$_z$ bands.