2 research outputs found
Energy gap and proximity effect in superconducting wires
Measurements of the penetration depth in the presence of a DC
magnetic field were performed in wires. In as-prepared wires shows a strong diamagnetic downturn below . A DC
magnetic field of completely suppressed the downturn. The data are
consistent with proximity coupling to a surface layer left during
synthesis. A theory for the proximity effect in the clean limit, together with
an assumed distribution of the layer thickness, qualitatively explains the
field and temperature dependence of the data. Removal of the by chemical
etching results in an exponential temperature dependence for with
an energy gap of (),
in close agreement with recent measurements on commercial powders and single
crystals. This minimum gap is only 44% of the BCS weak coupling value, implying
substantial anisotropy.Comment: RevTeX 4, 4 EPS figure