Condensation energy and spectral functions in high-temperature superconductors

If high-temperatures cuprate superconductivity is due to electronic correla tions, then the energy difference between the normal and superconducting st ates can be expressed in terms of the occupied part of the single-particle spectral function. The latter can, in principle, he determined from angle-r esolved photoemission (ARPES) data. As a consequence, the energy gain drivi ng the development of the superconducting state is intimately related to th e dramatic changes in the photoemission line shape when going below T-c. Th ese paints are illustrated in the context of the "mode'' model used to fit ARPES data in the normal and superconducting states, where the question of kinetic-energy versus potential-energy-driven superconductivity is explored in detail. We use our findings to comment on the relation of ARPES data to the condensation energy and to various other experimental data. In particu lar, our results suggest that the nature of the superconducting transition is strongly related to how anomalous (non-Fermi-liquid-like) the normal-sta te spectral function is and, as such, is dependent upon the doping level.