Hall effect and ghost critical field in disordered superconducting films

abstract-We observe a peak in the Hall resistance ocurring at a magnetic field H* in superconducting disordered thin films. Below the zero-field transition temperature Tc0, H* exactly tracks the upper critical field, Hc2, all the way to zero temperature. Near Tc0, H* becomes vanishingly small, while above Tc0 the peak again scales to higher fields as the temperature is further increased. Companion measurements of the fluctuation magnetoconductivity at temperatures above Tc0 allow precise and indpendent determination of the 'ghost critical field' Hgc, the field scale for suppression of superconducting fluctuations above Tc0. We find that H* and Hgc are distinct quantities but show similar scaling above Tc0, and compare these results to similar findings in studies of the Nernst effect in thin films [A. Pourret et al. Phys. Rev. B 76, 214504, (2007)] and high-temperature superconductors [J. Chang et al. Nature Physics 8, 751 (2012)].