The dependence of the hole spectrum on spin frustration and direct hopping in the two-band Hubbard model

The one-hole spectrum epsilon (k) in the CuO₂ plane is studied in the framework of the two-band Hubbard model with direct O-O hopping h. The finite O-hole concentration n is taken into account via the frustration alpha in the Cu spin subsystem. The epsilon (k) minimum position and Fermi surface topology strongly depend on the alpha - and h-values. The density of states has a sharp peak near the bottom of the band. The model demonstrates the non-rigid-band behaviour of epsilon (k) and Fermi level pinning observed in recent photoemission experiments on high-T_c superconductors.