Orbital Degeneracy and Peierls Instability in Triangular Lattice Superconductor Ir${}_{1-x}$Pt${}_x$Te${}_2$

Abstract

We have studied electronic structure of triangular lattice Ir${}_{1-x}$Pt${}_x$Te${}_2$ superconductor using photoemission spectroscopy and model calculations. Ir $4f$ core-level photoemission spectra show that Ir $5d$ $t_{2g}$ charge modulation established in the low temperature phase of IrTe${}_2$ is suppressed by Pt doping. This observation indicates that the suppression of charge modulation is related to the emergence of superconductivity. Valence-band photoemission spectra of IrTe${}_2$ suggest that the Ir $5d$ charge modulation is accompanied by Ir $5d$ orbital reconstruction. Based on the photoemission results and model calculations, we argue that the orbitally-induced Peierls effect governs the charge and orbital instability in the Ir${}_{1-x}$Pt${}_x$Te${}_2$.

5 pages,4 figures