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Giant anharmonicity and non-linear electron-phonon coupling in MgB$_{2}$; A combined first-principles calculations and neutron scattering study

T. Yildirim·O. Gulseren·J. W. Lynn·C. M. Brown·T. J. Udovic·H. Z. Qing·N. Rogado·K. A. Regan·M. A. Hayward·J. S. Slusky·T. He·M. K. Haas·P. Khalifah·K. Inumaru·R. J. Cava
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Abstract

We report first-principles calculations of the electronic band structure and lattice dynamics for the new superconductor MgB$_{2}$. The excellent agreement between theory and our inelastic neutron scattering measurements of the phonon density of states gives confidence that the calculations provide a sound description of the physical properties of the system. The numerical results reveal that the in-plane boron phonons (with E$_{2g}$ symmetry) near the zone-center are very anharmonic, and are strongly coupled to the partially occupied planar B $σ$ bands near the Fermi level. This giant anharmonicity and non-linear electron-phonon coupling is key to explaining the observed high T$_{c}$ and boron isotope effect in MgB$_{2}$

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T. Yildirim, O. Gulseren, J. W. Lynn, C. M. Brown, T. J. Udovic, H. Z. Qing, N. Rogado, K. A. Regan, M. A. Hayward, J. S. Slusky, T. He, M. K. Haas, P. Khalifah, K. Inumaru, R. J. Cava. 2001-04-26. Giant anharmonicity and non-linear electron-phonon coupling in MgB$_{2}$; A combined first-principles calculations and neutron scattering study. https://doi.org/10.1103/physrevlett.87.037001

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