Orbital degeneracy and Peierls instability in the triangular-lattice superconductor Ir1-xPtxTe2

We have studied the electronic structure of the triangular lattice Ir1-xPtxTe2 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 IrTe2 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 IrTe2 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 Ir1-xPtxTe2.