Electronic Density of States and Strong Electron–Phonon Coupling in Nb3Sn

Abstract

Using the Full-Potential non-orthogonal Local-Orbital Minimum-Basis Band-structure Scheme (FPLO) coupled with the XFSF program for unconventional superconductor Nb3Sn, we perform simultaneously the Bravais lattice, the density of states (DOS), the band structure and the Fermi surface (FS) topology. The density of states shows a large number of peaks of width on the order of 20 eV near the Fermi level which is found to be dominated by Nb-4d states, contributing about 90% of the bare DOS. The electron–phonon coupling constant λ ep is estimated to be about 1.46, which indicates that Nb3Sn is a strongly coupled superconductor. The two-dimensionality (2D) of the computed Fermi surface is another proof of the pronounced strength of this coupling. On the other hand, the discrepancy between the Debye temperature Θ D as previously obtained experimentally (Θ D=234 K) and that given by our band-structure calculations (Θ D=300.2 K) may originate from a phonon anisotropy likely generated by the anisotropic electron–phonon coupling.