Absence of nesting in the charge-density-wave system1T-VS2as seen by photoelectron spectroscopy

Abstract

We report on the electronic structure and Fermi surfaces of the transition-metal dichalcogenide $1{\text{T-VS}}_{2}$ in the low-temperature charge-density-wave (CDW) ordered phase. Using soft x-ray angle-resolved photoemission spectroscopy (ARPES), we investigate the in-plane and out-of-plane vanadium- and sulfur-derived band dispersions and identify ${k}_{z}$ dispersions in this layered system. Core-level photoemission and x-ray absorption spectroscopy show that vanadium electrons are in the ${d}^{1}$ configuration while $2p\text{\ensuremath{-}}3d$ resonant ARPES shows only $3d$-derived dispersive bands near the Fermi level. Comparison of energy- and angle-dependent data with band-structure calculations reveals renormalization of the $3d$ bands, but no lower Hubbard band, a signature of the rather weak electron-electron correlations in ${\text{VS}}_{2}$. High-resolution temperature-dependent low-energy ARPES measurements show the opening of an energy gap at the Fermi level that is attributed to the condensation of the CDW phase. The results indicate a CDW transition in the absence of nesting for $1{\text{T-VS}}_{2}$