CALCULATION OF ANGLE-RESOLVED PHOTOEMISSION AND TUNNELING FOR A CUO2 LAYER IN THE NORMAL AND SUPERCONDUCTING STATES

We represent the normal-state electronic structure of a CuO2 layer in terms of a three-band model having an infinite Cu intrasite Coulomb re pulsion. We express the Lagrangian for this model using a slave-boson formalism and approximate it in a large-N expansion to order 1/N in th e zero-temperature limit. The angle-resolved spectral weight determine d from the resulting Green's functions suggests that within this pictu re higher-order corrections in 1/N are necessary for good agreement wi th the corresponding angle-resolved photoemission data. We phenomenolo gically add spin-dependent Heisenberg interactions between neighboring Cu sites and neighboring Cu and O sites. These interactions form the basis of a nonretarded calculation of the superconducting state. For t he case of an interaction between neighboring Cu spins only, the lowes t-energy solution possesses d(x2 - y2) symmetry. The use of a three-ba nd model leads to the possibility of the addition of the interaction b etween Cu and O spins. The resulting d + idp superconducting state inv olves pairing of carriers in Cu orbitals both with themselves and with holes on the O orbitals. This additional pairing will remove the node in the d-wave state at T = O by an amount that depends on the Cu-O co upling parameter; however, the mixed-symmetry state occurs only for a narrow range of coupling parameters. The angle-resolved photoemission and tunneling results are calculated and compared to experimental find ings.