An Integrated First-Principles and Many-Body Theory Description of Electron-Phonon Superconductors

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9627778 Freericks/Liu This grant supports a new program, consisting of two young faculty members, one female (A. Liu) in condensed matter physics at the Georgetown University. The grant supports work on a careful and detailed analysis of the electron- phonon interaction based theory of superconductivity in the regimes where Migdal's theorem is no longer valid. This work also takes advantage of new theoretical tools that have been developed for many body problems in large dimensions (or alternatively large coordination number for atoms). The work proposed here includes first principles calculation of the spectral densities (SD), derivation of SD from the experimental tunneling data using more accurate algorithm, incorporate vertex corrections in the theory of superconductivity and analyze the effects of lattice anharmonicity. %%% This grant is to support collaborative research of two young faculty (one female) with complementary interests and expertise in the theory of superconductivity at Georgetown University. A major difference between the conventional superconductors and essentially all of the ones that have been discovered recently (doped fullerenes, high Tc materials) is that the theoretical framework, so successful in elucidating superconductivity in conventional materials, cannot be applied to the new materials. This project is to consider the associated difficulties and find solutions for them. ***