Doping-dependent electronic structure of cuprates studied using angle-scanned photoemission

Full k(parallel to)-maps of the electronic structure near the Fermi level o f differently doped cuprates measured with angle-scanned photoelectron spec troscopy are presented. The valence band maximum of the antiferromagnetic i nsulator Sr2CuO2Cl2, which is taken as a representative of an undoped cupra te, and the Fermi surfaces of overdoped, optimally doped and underdoped Bi2 Sr2CaCu2O8+delta high-temperature superconductors are mapped in the normal state. The results confirm the existence of large Luttinger Fermi surfaces at high doping with a Fermi surface volume proportional to (1 + x), where x is the hole concentration. At very low doping, however, we find that this assumption based on Luttinger's theorem is not fulfilled. This implies a ch ange in the topology of the Fermi surface. Furthermore the intensity of the shadow bands observed on the Fermi surface of Bi2Sr2CaCu2O8+delta as a fun ction of the doping is discussed.