Quasiparticles and photoemission spectra in correlated fermion systems

We present some selected numerical results for the spectral function of two models currently discussed for HTSC. For the t-J model we find a quasiparticle band with dispersion ε{lunate}k→ ≈ J 2(cos kx + cos ky)2 well separated from a broad continuum of states (7t). For the Emery model photoemission and inverse photoemission spectra for the insulating (undoped) and for doped cases are discussed. In the doped case new states with strong O-character appear in the charge transfer gap, which appear to be responsible for conductivity in hole-doped HTSC. © 1989.