Observation of a Phase-Dependent Conductivity in Superconducting Point Contacts

Abstract

Measurements of the impedance of phase-biased superconducting point contacts are interpreted in terms of the Josephson expression for the total current, $i={i}_{c}sin\ensuremath{\phi}+{G}_{0}(1+\ensuremath{\alpha}\ifmmode\times\else\texttimes\fi{}cos\ensuremath{\phi})V$. The data give good agreement with this expression and yield a parametric inductance $\mathcal{L}(\ensuremath{\phi})=\frac{\ensuremath{\hbar}}{2e{i}_{c}cos\ensuremath{\phi}}$ and a phase-dependent conductance $G(\ensuremath{\phi})={G}_{0}(1+\ensuremath{\alpha}cos\ensuremath{\phi})$, with $\ensuremath{\alpha}\ensuremath{\approx}\ensuremath{-}1$.