Complete k-space mappings of cuprates at different doping levels

We present full Fermi surface maps of differently doped Bi 2 Sr 2 CaCu 2 O 8+ x crystals measured with angle-resolved photoemission. We find, for overdoped and optimally doped samples, a large Fermi surface centered at ( π , π ). For an underdoped sample with a T c of 30K the contours of a large Fermi surface are still visible, but the photoelectron intensity is strongly reduced around ( π ,0). The valence band maximum of the undoped antiferromagnetic insulator Sr 2 CuO 2 Cl 2 forms maxima at ( π /2, π /2) and equivalent points.