Abstract
We investigate the upper critical field in a dirty two-band superconductor within quasiclassical Usadel equations. The regime of very high anisotropy in the quasi-2D band, relevant for is considered. We show that strong disparities in pairing interactions and diffusion constant anisotropies for two bands influence the in-plane in a different way at high and low temperatures. This causes temperature-dependent anisotropy, in accordance with recent experimental data in The three-dimensional band most strongly influences the in-plane near in the Ginzburg-Landau (GL) region. However, due to a very large difference between the c-axis coherence lengths in the two bands, the GL theory is applicable only in an extremely narrow temperature range near The angular dependence of deviates from a simple effective-mass law even near
- Received 11 March 2003
DOI:https://doi.org/10.1103/PhysRevB.68.104503
©2003 American Physical Society