HOLE-DOPED CUPRATES - FROM SMALL TO LARGE FERMI-SURFACE

A strong-coupling-limit theory of the normal-state hole dynamics in co pper oxide superconductors is developed. The theory is based on the t- t'-J model and the diagrammatic technique for Hubbard operators. We ha ve analyzed the evolution of the hole dynamics with doping and have fo und that the Fermi surface of the itinerant quasiparticles changes abr uptly at low doping from small with volume proportional to the concent ration of doped holes delta to large with a volume proportional to 1 delta. The ground state with the small Fermi surface is unstable agai nst long-range antiferromagnetic ordering. The state with a large Ferm i surface is characterized by a close disposition of the Fermi level a nd of the saddle-point singularity within an extended range of doping, delta = 0.1-0.4. The results account well for the data of angle-resol ved photoemission experiments, Some effects of an electronic topologic al phase transition occurring at delta = delta(c) (the doping which co rresponds to the intersection of the Fermi level and the saddle-point singularity) on the physical properties are discussed.