Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 18: Superconductivity - Properties, Electronic Structure, Order Parameter II

TT 18.4: Vortrag

Montag, 7. März 2005, 11:00–11:15, TU H2053

Band filling and interband scattering effects in MgB₂: C vs Al doping — •Jens Kortus¹, O.V. Dolgov², R.K. Kremer², and A.A. Golubov³ — ¹Institut de Physique et Chimie des Matériaux de Strasbourg, 23 rue du Loess, F-67034 Strasbourg Cedex 2, France — ²MPI-FKF, Heisenbergstr. 1, 70569 Stuttgart — ³MESA+ Research Institute and Faculty of Science and Technology, University of Twente, 7500 AE Enschede, The Netherlands

We argue, based on band structure calculations and 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 λ by the variation of the density of states as 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 π gap as function of doping by a compensation of the effect of band filling and interband scattering. Both effects together generate a nearly constant π 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.