Quasiparticle spectra of high-temperature superconductors

We present a semiphenomenological approach to calculating the quasiparticle spectra of high-temperature superconductors (HTSC's). It is based on a particularly efficient parametrisation of the effective electron-electron interaction afforded by the density-functional theory for superconductors and a tight-binding linearized-muffin-tin-orbital scheme for solving the corresponding Kohn-Sham-Bogoliubov-de Gennes equations. We illustrate the method by investigating a number of site and orbital specific, but otherwise phenomenological, models of pairing in quantitative detail and discuss the results using BCS-like theory and insights to the HTSC band structures. We compare our results for the gap function on the Fermi surface with those deduced from photoemission experiments on single crystals of YBa2Cu3O7. We also compare our predictions for the temperature dependence of the specific heat with measurements and conclude, provisionally, that the dominant pairing interaction operates between electrons of opposite spin, on nearest-neighbor Cu sites in d(x2-y2) orbitals. [S0163-1829(98)04426-4].