An J M, Pickett W E
Department of Physics, University of California, Davis, California 95616, USA.
Phys Rev Lett. 2001 May 7;86(19):4366-9. doi: 10.1103/PhysRevLett.86.4366.
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.
对MgB₂及相关等电子体系的一系列计算表明，与石墨相比，Mg²⁺离子层使非键合B π（p(z)）能带相对于键合σ（sp(x)p(y)）能带降低，导致σ→π电荷转移和每个晶胞0.13个空穴的σ能带掺杂。由于其二维特性，σ能带对费米能级态密度有很大贡献。计算得到的Γ点声子的形变势表明，B键的拉伸模式主导了电声子耦合。由σ能带空穴驱动的超导性与用Al掺杂破坏超导性的报道一致。
