Low temperature dependence of the penetration depth in superconductor MgB2 in the presence and absence of impurities

The large variety of the measured magnetic penetration depth is interpreted by using two microscopic gap models. We calculate the penetration depth of superconductor MgB2 in low temperatures by using two gap and an anisotropic S-wave gap models. In the two gap model we consider that the total penetration depth is a weighted sum of the contribution from sigma- and pi-bands and the interaction between these two bands is ignored. The effect of impurities on the or-band is less than that pi-band and there are tremendous modifications of the temperature dependence of the penetration depth for pi-band.