Complete k-space mappings of cuprates at different doping levels

We present full Fermi surface maps of differently doped Bi2Sr2CaCu2O8+x cry stals measured with angle-resolved photoemission. We find, for overdoped an d optimally doped samples, a large Fermi surface centered at (pi, pi). For an underdoped sample with a T-c of 30K the contours of a large Fermi surfac e are still visible, but the photoelectron intensity is strongly reduced ar ound (pi,0). The valence band maximum of the undoped antiferromagnetic insu lator Sr2CuO2Cl2 forms maxima at (pi/2,pi/2) and equivalent points. (C) 199 8 Elsevier Science Ltd. All rights reserved.