A SIMPLE THEORY OF ANGLE-RESOLVED PHOTOEMISSION SPECTROSCOPY CROSS-SECTIONS WITH APPLICATIONS TO YBA2CU3O7 AND SR2RUO4

Vie try to interpret angle-resolved photoemission spectroscopy (ARPES) cross sections directly in band-structure terms by approximating the one-particle propagator needed to evaluate the lowest-order Keldysh di agram using the bulk Green function. As applications to YBa2Cu3O7 and Sr2RuO4 demonstrate, this is a sensible approach, since it reproduces important features of experimental curves. Matrix element effects stro ngly enhancing the contributions of individual bands at certain energi es and depressing them at others are well described. Self-energy corre ctions included in an average way improve the agreement and allow for a rough estimate of the magnitude of the band broadening. in the case of YBa2Cu3O7 our investigations demonstrate the significance of correl ations, since adding self-interaction corrections to the local density approximation leads to considerable improvement of the calculated ARP ES cross sections.