QUASI-PARTICLE DISPERSION OF THE INSULATING COPPER-OXIDE SR2CUO2CL2 BY EMPLOYING VERTICAL AND HORIZONTAL DOUBLE HOPPINGS

By adding horizontal and vertical double hoppings to the t-t'-J Hamilt onian, we can reproduce the experimentally determined quasiparticle di spersion data for Sr2CuO2Cl2 reasonably well (in both shape and bandwi dth) in most of the Brillouin zone. These numerical results have been obtained by using the self-consistent noncrossing approximation. An al ternative simplified calculation using first-order perturbation theory gives closely similar results. The strong coupling to magnons plays a n important role in guaranteeing a reasonable bandwidth and reproducin g the observed peak strength of the photoemission spectrum. The presen t study indicates the importance of the horizontal and vertical double hoppings in fitting various experimental results within the one-band model.