title: Band filling and interband scattering effects in MgB2: carbon versus aluminum doping.
abstract: We argue, based on band structure calculations and the Eliashberg theory, that the observed decrease of T(c) of Al and C doped MgB2 samples can be understood mainly in terms of a band filling effect due to the electron doping by Al and C. A simple scaling of the electron-phonon coupling constant lambda by the variation of the density of states as a function of electron doping is sufficient to capture the experimentally observed behavior. Further, we also explain the long standing open question of the experimental observation of a nearly constant pi gap as a function of doping by a compensation of the effect of band filling and interband scattering. Both effects together generate a nearly constant pi gap and shift the merging point of both gaps to higher doping concentrations, resolving the discrepancy between experiment and theoretical predictions based on interband scattering only.
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Kortus
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Dolgov
authors.forename: Reinhard K
authors.initials: RK
authors.lastname: Kremer
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Golubov