Phonons and Electronic Excitations in the Superconducting Cuprates: Analytical and Numerical Studies Focused on Raman Scattering

Goal of the project: Self-consistent comprehensive investigation of low-energy excitations (electrons and phonons) in high-temperature superconductors for realistic band structure models both in the normal and superconducting states. Development of a picture of Raman scattering by low-energy excitations in the normal and superconducting states in presence of electron-phonon coupling and electronic correlations. Problems included in the research plan: Problem 1. Self-consistent picture of electronic excitations and phonons due to electron-phonon coupling and electronic correlations in the normal and superconducting state of cuprate superconductors. Problem 2. Raman scattering by phonons and electronic excitations in different electron-phonon coupling and electronic correlations regimes in the normal and superconducting states. Investigation techniques: Feynman diagram approach on the basis of the theory of strongly-coupled superconductors, numerical analysis using the generalized gradient approximation on the basis of developed WIEN95 computer codes. The results expected: 1. spectra of low-energy excitations in the superconducting cuprates above and below the transition temperature, 2. picture of Raman scattering in cuprate superconductors under strong electron-phonon coupling.