Magnetic Field Effects on the Electrical Conductivity The to Fluctuations Of the Superconducting Order Parameter Above T-c

The electrical conductivity above the transition temperature T-c due to fluctuations of the superconducting order parameter has been measured in aluminum films in the presence of a magnetic field (parallel and perpendicular to the film surface), as well as in the absence of a magnetic field. It has been found, in particular from the results in a perpendicular magnetic field, that the Aslaniazov-Laikin theory (AL) and its extension can be applied for temperatures close to T-c. A deviation from the theoretical linear relation (AL) sigma(n)/sigma(T) similar to ln(T/T-c) in zero and parallel field might be explained in terms of the Maki Thompson model (M T), which is consistent with previous experiments in Al films. However, the transition width due to fluctuations in a perpendicular magnetic field is not always enhanced, contrary to the prediction of the MT model. Even in the cases in which they are enhanced, the transition width is smaller than the value predicted by the MT model.