Conductance characteristics between a normal metal and a clean superconductor carrying a supercurrent

Abstract

The effect of a transverse supercurrent ${I}_{s}$ up to the thermodynamic critical current on the low-temperature conductance characteristics between a normal metal $N$ and a clean $s$- or $d$-wave superconductor $(S)$ is theoretically investigated, covering from metallic contact $(z=0)$ to the tunneling limit $(z⪢1)$. For $d$-wave $S$ both (100) and (110) contacts are studied. Many features found are due to current-induced gap anisotropy and requires $S$ to be in the clean limit. Near critical ${I}_{s}$ and for $z\ensuremath{\simeq}1$, a three-humped structure appears for both $s$-wave $S$ and $d$-wave $S$ with (100) contact, signaling onset of current-induced gaplessness on the Fermi surface where gap originally exists.