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

The superconducting phase transition of the conventional A15 superconductor V3Si occurs at a transition temperature of T-c=17.1 K. According to the BC S theory, the zero-temperature gap width in the electronic density of state s (DOS) is given by 1.75k(B)T(c) = 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 photoemis sion spectroscopy (PES) with an instrumental energy resolution of 3 meV (mo nochromatized He I). For the first time in photoemission spectra on a conve ntional 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 oth er experimental methods. (C) 2001 Elsevier Science B.V. All rights reserved .