Microwave response of

Abstract

The investigation of the temperature dependences of microwave surface impedance and complex conductivity of V3Si single crystals with different stoichiometry allowed to observe a number of peculiarities which are in remarkable contradiction with single-gap Bardeen-Cooper-Schrieffer theory. At the same time, they can be well described by the two-band model of superconductivity, thus strongly evidencing the existence of two distinct energy gaps with zero-temperature values $\Delta_1\approx 1.8\,T_c$ and $\Delta_2\approx 0.95\,T_c$ in \chem{V_3 Si}