Temperature dependence of the optical conductivity and penetration depth in superconductor MgB2 film

By using Green`s function method the temperature dependence of the optical conductivity and penetration depth of high-quality MgB2 film are calculated in the framework of the two-band model. We compare our results with experimental data and we argue that the single gap model is insufficient to describe the optical and penetration depth behavior, but the two-band model with different symmetries describes the data rather well. In the two gap model we consider that the both components of optical conductivity are a weighted sum of the contribution from σ and π bonds and hybridization between them is negligible.