Bond-Order and the Role of Ligand States in Stripe-Modulated IrTe2

TL;DR

This study investigates the electronic and structural modulations in IrTe$_2$ using x-ray spectroscopy, revealing the importance of covalent Te 5$p$-Ir 5$d$ bonds in stripe order and their potential link to exotic phases like those in cuprates.

Contribution

It uncovers the role of covalent Te 5$p$-Ir 5$d$ bonds in stripe order and their coupling with charge and orbital order, providing new insights into IrTe$_2$'s electronic structure.

Findings

Te 5$p$-Ir 5$d$ covalent states near Fermi level

Enhanced REXS signal at superlattice reflection below 280 K

Coupling of bond-density modulation with charge/orbital order

Abstract

The coupled electronic-structural modulations of the ligand states in IrTe$_2$ have been studied by x-ray absorption spectroscopy (XAS) and resonant elastic x-ray scattering (REXS). Distinctive pre-edge structures are observed at the Te-$M_{4,5}$ (3$d$ $\rightarrow$ 5$p$) absorption edge, indicating the presence of a Te 5$p$-Ir 5$d$ covalent state near the Fermi level. An enhancement of the REXS signal near the Te 3$d$ $\rightarrow$ 5$p$ resonance at the $Q\!=\!(1/5,0,-1/5)$ superlattice reflection is observed below the structural transition temperature $T_s\sim$ 280 K. The analysis of the energy-dependent REXS lineshape reveals the key role played by the spatial modulation of the covalent Te 5$p$-Ir 5$d$ bond-density in driving the stripe-like order in IrTe$_2$, and uncovers its coupling with the charge and/or orbital order at the Ir sites. The similarity between these findings and the charge-ordering phenomenology observed in the high-T$_c$ superconducting cuprates suggests that the iridates may harbor similar exotic phases.