Anisotropic s-wave superconductivity in MgB2:: comparison with experiments on optical properties

We have evaluated the optical conductivity and transmittance for the two-band superconductor MgB2. We show that a single-band anisotropic model is not sufficient to understand consistently the optical and thermodynamic behaviors. The transmittance measured for MgB2 thin film is well explained by the two-band model with different anisotropies in contrast to the single-band anisotropic model. In our model the pairing symmetry in each band has anisotropic character; the Cooper pair in sigma-band has the anisotropy in the ab-plane and the pair in pi-band has the prolate form possessing anisotropy in the c-direction. Our model is also consistent with thermodynamic quantities such as the specific heat jump and the critical magnetic field reduction. (C) 2003 Elsevier B.V. All rights reserved.