Resistive transitions of thin film superconductors in a magnetic field

The effect of fluctuations on the resistive transition of superconducting thin films of various thicknesses in a perpendicular magnetic field is analyzed in terms of the continuous expressions derived by Ullah and Dorsey. We studied the dimensionality and the functional dependence of the scaling procedure suggested by theory. We find good agreement in the paraconducting regime (B>${\mathrm{B}}_{\mathrm{c}2\mathrm{}}$) but clear deviations in the flux-flow regime (B<${\mathrm{B}}_{\mathrm{c}2\mathrm{}}$) illustrating the shortcomings of the Hartree approximation. We also discuss the effects of flux pinning on the melting transition for the thinnest film and compare our results with recent work on an a-${\mathrm{NbO}}_{\mathrm{x}}$ film of comparable thickness. We see no evidence for the suggestion put forward by Nikulov, Remisov, and Oboznov that a vortex solid does not exist down to very low fields.