The transport properties of superconducting single crystal Pb nanowires that are 55 and 70 nm in diameter were studied by the standard four-electrode method. With normal metal electrodes, resistance-temperature and resistance-magnetic field scans show a series of resistance steps with increasing temperature and magnetic field as the wires are brought toward the normal state. The resistance-current ($R$-$I$) scans at different temperatures and magnetic fields show that the increase in $R$ with $I$ is punctuated with sharp steps at specific current values. A large residual resistance is observed down to 2 K. The origin of these phenomena is related to the inhomogeneity and proximity effect from the normal electrodes.

• Received 29 January 2012

DOI:https://doi.org/10.1103/PhysRevB.86.035439