title: Superconductivity of MgB2: covalent bonds driven metallic.
abstract: A series of calculations on MgB2 and related isoelectronic systems indicates that the layer of Mg2+ ions lowers the nonbonding B pi ( p(z)) bands relative to the bonding sigma ( sp(x)p(y)) bands compared to graphite, causing sigma-->pi charge transfer and sigma band doping of 0.13 holes/cell. Because of their two dimensionality the sigma bands contribute strongly to the Fermi level density of states. Calculated deformation potentials of gamma point phonons identify the B bond stretching modes as dominating the electron-phonon coupling. Superconductivity driven by sigma band holes is consistent with the report of destruction of superconductivity by doping with Al.
authors.affiliation: Department of Physics, University of California, Davis, California 95616, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: An
authors.forename: W E
authors.initials: WE
authors.lastname: Pickett