Anomalous temperature dependence of the upper critical magnetic field in Bi-Sr-Cu-O

Abstract

${\mathit{H}}_{\mathrm{c}2}$(T) has been measured for thin BSCO films over a larger combined range of magnetic field and reduced temperature than for any other superconductor. ${\mathit{H}}_{\mathit{c}2}$(T) diverged anomalously as the temperature decreased: At the lowest temperature, it was 5 times that expected for a conventional superconductor. Such a strong divergence cannot be explained by any conventional model.