DOPING-DEPENDENT QUASI-PARTICLE BAND-STRUCTURE IN CUPRATE SUPERCONDUCTORS

We present an exact diagonalization study of the single-particle spect ral function in the so-called t-t'-t ''-J model in two dimensions. As a key result, we find that hole doping leads to a major reconstruction of the quasiparticle band structure near (pi,0): whereas for the undo ped system the quasiparticle states near (pi,0) are deep below the top of the band near (pi/2,pi/2), hole doping shifts these states up to E (F), resulting in extended flat band regions close to E(F) and around (pi,0).