Band filling and interband scattering effects in MgB${}_2$: C vs Al doping

Abstract

We argue, based on band structure calculations and Eliashberg theory, that the observed decrease of $T_c$ of Al and C doped MgB${}_2$ 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 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 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.

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• de Haas-van Alphen effect investigations of the electronic structure of pure and aluminum-doped MgB_2
• Theory of vortices in hybridized ballistic/diffusive-band superconductors
• Ab initio modeling of superconducting alloys
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• Application prospects of MgB${}_2$ in view of its basic properties
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• Effects of magnetic and non-magnetic doping on the vortex lattice in MgB${}_2$
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• Enhancing long-range order in disordered two-band s-wave superconductors