Anomalous transverse voltages in the superconducting surface sheath

The critical state and transport properties of the superconducting sheath are investigated, in slabs parallel to the applied magnetic field, when it makes an arbitrary angle θ with the direction of the applied current. The observation of critical currents governed by surface defects, and linear current-voltage characteristics, corroborate the conclusion advanced by several authors in the past, that the surface sheath of a real rough surface is populated by quantized vortices or ''flux spots,'' which should exhibit the same pinning and flux-flow properties as usual vortices. Nevertheless, transverse voltages measured above Hc2 are at variance with the well-known general relation between macroscopic fields, E=-vLxB, contrary to those observed in the mixed state. Making allowance for the observed anisotropy of the surface critical current in parallel field, a model is proposed that accounts successfully for the unexpected distribution of electric currents and fields above Hc2. We emphasize that experimental results cannot be reconciled with the existence of surface vortices, and our analysis would lead to serious difficulties in interpreting Joule dissipation, unless we rely on some unorthodox conclusions of a continuum theory of vortex motion developed recently by two of us. Measurements reported in this paper support the correctness of this theory