Electron-phonon coupling and two-band superconductivity of Al- and C-doped MgB2

Abstract

We have studied the electron-phonon and superconducting properties of the Mg{1-x}AlxB2 and MgB{2(1-y)}C{2y} alloys within the framework of density functional theory using the self-consistent virtual-crystal approximation. For both alloys, the Eliashberg spectral functions and the electron-phonon coupling constants have been calculated in the two-band model for several concentrations up to x(Al)=0.55 and y(C)=0.175. We solved numerically the two-band Eliashberg gap equations without considering interband scattering. Using a single parameter for the Coulomb pseudopotential, which was determined for the undoped compound, we were able to reproduce the experimental doping dependence of Delta_sigma, Delta_pi, and T_c for both alloys on a quantitative level. In particular, the observed differences in the doping range of superconductivity between Al and C doping indicate a pronounced influence of the doping site, which can be explained naturally in the present approach without the need to invoke interband scattering, suggesting that this factor plays only a minor role.

18 pages, 6 figures

References in corpus (5)

• Band filling and interband scattering effects in MgB${}_2$: C vs Al doping
• Al substitution in MgB2 crystals: influence on superconducting and structural properties
• Influence of Al doping on the critical fields and gap values in magnesium diboride single crystals
• On Heavy Carbon Doping of MgB${}_2$
• Point-contact Andreev-reflection spectroscopy in segregation-free Mg_{1-x}Al_{x}B_2 single crystals up to x=0.32

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• A first-principles study of superconductivity on RbH by doping without applied pressure
• Electron-phonon coupling and superconductivity in $\alpha$-MoB${}_2$ as a function of pressure
• First-Principles Calculation of Superconducting $T_c$ in Superhard B-C-N Metals