Proceedings of the Physical Society · 1966 · 27 citations · 12 references
Superconducting MaterialEngineeringBismuth-based SuperconductorsThin Type IiSurface SuperconductivityMagnetoresistanceCritical CurrentsTunneling MicroscopyNovel SuperconductorsSuperconductivityQuantum MaterialsHigh Tc SuperconductorsSuperconducting DevicesHigh-tc SuperconductivityPhysicsFluxon EntryHigh-temperature SuperconductivityFilm ThicknessApplied PhysicsCondensed Matter PhysicsThin FilmsQuantum Superconductivity
Electron tunnelling from a normal metal into thin type II superconducting films (Pb-In 20 wt%) has been studied as a function of magnetic field H and film thickness (600-7000 Å) at 4.2 and 1.5 °K. The behaviour at high field confirms the work of Tomasch: surface superconductivity is quenched at Hc2, the upper critical field, when H is perpendicular to the film surface, but persists to Hc3, the surface sheath critical field, in a parallel field (H||). The degree of surface conductivity is characterized by a current profile ΔI, defined by the tunnel junctions' (I, V) characteristics. For films thicker than 1000 Å, a plot of ΔI against H|| exhibits a series of dips which is dependent on film thickness and temperature. At fields where this structure is present, hysteresis is found in decreasing H. The structure and hysteresis are attributed to entry and exit of fluxons from the films.
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