Multiband conductivity and a multigap superconducting phase in V3Si films from optical measurements at terahertz frequencies

The possibility of multiband conductivity and multigap superconductivity is explored in oriented ${\text{V}}_{3}\text{Si}$ thin films by means of reflectance and transmittance measurements at terahertz frequencies. The temperature dependence of the transmittance spectra in the normal state gives evidence of two bands contributing to the film conductivity. This outcome is consistent with electronic structure calculations performed within density functional theory. On this basis, we performed a detailed data analysis and found that all optical data can be consistently accounted for within a two-band framework, with the presence of two optical gaps in the superconducting state corresponding to $2\ensuremath{\Delta}/k{T}_{c}$ values close to 1.8 and 3.8.