On Heavy Carbon Doping of MgB$_2$

Deepa Kasinathan; K. -W. Lee; W. E. Pickett

doi:10.1016/j.physc.2005.05.002

paper

On Heavy Carbon Doping of MgB $_{2}$

arXiv:cond-mat/0409563 · doi:10.1016/j.physc.2005.05.002

Abstract

Heavy carbon doping of MgB $_{2}$ is studied by first principles electronic structure studies of two types, an ordered supercell (Mg(B $_{1 - x}$ C $_{x}$ ) $_{2}$ ,x=0.0833) and also the coherent potential approximation method that incorporates effects of B-C disorder. For the ordered model, the twofold degenerate $σ$ -bands that are the basis of the high temperature superconductivity are split by 60 meV (i.e.7 meV/%C) and the $σ$ Fermi cylinders contain 0.070 holes/cell, compared to 0.11 for MgB $_{2}$ . A virtual crystal treatment tends to overestimate the rate at which $σ$ holes are filled by substitutional carbon. The coherent potential approximation (CPA) calculations give the same rate of band filling as the supercell method. The occupied local density of states of C is almost identical to that of B in the upper 2 eV of the valence bands, but in the range -8 eV to -2 eV, C has a considerably larger density of states. The calculations indicate that the $σ$ Fermi surface cylinders pinch off at the zone center only above the maximum C concentration x ~ 0.10. These results indicate that Mg(B $_{1 - x}$ C $_{x}$ ) $_{2}$ as well as Mg $_{1 - x}$ Al $_{x}$ B $_{2}$ is a good system in which to study the evolution of the unusual electron-phonon coupling character and strength as the crucial $σ$ hole states are filled.

8 pages, 8 figures

On Heavy Carbon Doping of MgB $_{2}$

Abstract

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Cited by in corpus (4)

On Heavy Carbon Doping of MgB2​

Abstract

References in corpus (15)

Cited by in corpus (4)

On Heavy Carbon Doping of MgB $_{2}$