Investigation of the BCS density of states on a conventional superconductor by high-resolution photoelectron spectroscopy

Abstract

Abstract The superconducting phase transition of the conventional A15 superconductor V3Si occurs at a transition temperature of Tc=17.1 K. According to the BCS theory, the zero-temperature gap width in the electronic density of states (DOS) is given by 1.75kBTc=2.5 meV, a value which is by a factor of the order of ten smaller than for High Temperature Superconductors (HTSC). We have investigated the DOS on polycrystalline V3Si surfaces by photoemission spectroscopy (PES) with an instrumental energy resolution of 3 meV (monochromatized He I). For the first time in photoemission spectra on a conventional superconductor, we could clearly detect the opening of a gap around the Fermi level and the signatures of the BCS DOS on this energy scale. A quantitative analysis of the data — based on a least-squares modelation by the theoretical BCS DOS — is in excellent agreement with the results of other experimental methods.