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Superconductivity of MgB2: Covalent Bonds Driven Metallic

J. M. An·W. E. Pickett
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Abstract

A series of calculations on MgB2 and related isoelectronic systems indicates that the layer of Mg(2+) ions lowers the non-bonding B "pi" (p_z) bands relative to the bonding "sigma" (sp_xp_y) bands compared to graphite, causing sigma --> pi charge transfer and sigma band doping of 0.13 holes/cell. Due to 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.

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J. M. An, W. E. Pickett. 2001-03-05. Superconductivity of MgB2: Covalent Bonds Driven Metallic. https://doi.org/10.1103/physrevlett.86.4366

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