Absence of nesting in the charge-density-wave system 1T-VS2 as seen by photoelectron spectroscopy

We report on the electronic structure and Fermi surfaces of the transition-metal dichalcogenide 1T-VS2 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-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 VS2. 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 1T-VS2