Investigation by Electron Tunneling of the Superconducting Energy Gaps in Nb, Ta, Sn, and Pb

Abstract

Electron tunneling between two superconductors separated by a thin potential barrier gives rise to nonlinear current vs voltage characteristics, from which a direct measurement of their energy gaps can be obtained. The temperature dependence of the $I:V$ characteristics for sandwiches of Ta/barrier/Pb and Nb/barrier/Sn has been studied and the energy gaps of tin and tantalum determined up to their transition temperatures. Good agreement has been obtained between the temperature dependence observed experimentally, and the predictions of the Bardeen, Cooper, and Schrieffer (BCS) theory of superconductivity.