Abstract
We investigate the influence of inhomogeneity in the pairing coupling constant on dirty BCS superconductors, focusing on , the order parameter , and the energy gap . Within mean-field theory, we find that when the length scale of the inhomogeneity is comparable to or larger than the coherence length, the ratio is significantly reduced from that of a homogeneous superconductor, while in the opposite limit, this ratio stays unmodified. In two dimensions, when strong phase fluctuations are included, the Kosterlitz-Thouless temperature is also studied. We find that when the inhomogeneity length scale is much larger than the coherence length, can be larger than the usual BCS value. We use our results to qualitatively explain recent experimental observation of a surprisingly low value of in thin films.
1 More- Received 18 December 2007
DOI:https://doi.org/10.1103/PhysRevB.77.144523
©2008 American Physical Society