Quantum localization and quantum interference effects in the magnetoconductivity of superconductors

Abstract

A model is presented to calculate the magnetoconductivity of three-dimensional aluminium films with various degrees of disorder in a wide range of magnetic fields. The argument is based on the effects of disorder on the electron dynamics of the supercarriers at low temperatures. When the average distance d _i between defects is much larger than the coherence length, the disorder appears highly inhomogeneous and superconductivity is auenched in a non-uniform fashion. On the other hand, when the superconducting coherence length ∂ of the material is of the same order as d _i, a auasihomogeneous type II domain at low fields dominated by disorder exists. In the high-field regime the superconducting coherence length is smaller than the distance d _i between defects, the medium is microscopically homogeneous on the scale of the coherence length and the structure of the disorder is unimportant. In this domain, as the field increases, the coherence length becomes smaller and the sample becomes microscopically even more uniform. In this case, electron motion is not impeded by scattering and the conductivity increases as the field increases. The analysis shows that, in the low-field regime, the behaviour of the magnetoconductivity with the applied field, which cannot be explained by existing theories, has an H ^−5/2 dependence. In the high-field regime, the magnetoconductivity deviates from the H ^½ dependence, which indicates the existence of additional contributions other than the weak localization and electron-electron interaction.