Determining accurate superconducting tunneling energy gaps: Anisotropy in single-crystal Nb

Abstract

Superconducting tunneling experiments on niobium single crystals with indium and lead‐bismuth counterelectrodes show an isotropic energy‐gap value of 3.12±0.05 meV, or 3.93kT_c, for 26 junction orientations. Self‐consistent analysis criteria have been developed for the determination of gap values. These criteria are not met in the existing literature on transition‐metal tunneling.