EVOLUTION OF THE ELECTRONIC-STRUCTURE WITH DOPING IN BI2SR2CACU2O8- ANGLE-RESOLVED PHOTOEMISSION RESULTS(DELTA )

We present experimental results showing that the electronic strucure o f the high Tc cuprate superconductors evolves from having large pieces of Fermi surface (FS) at high doping levels to small pieces of FS cen tered at (pi/2,pi/2) at low doping levels. The dramatic change in the FS occurs with only subtle changes in the electronic structure, which occur mostly near the (pi,0) point of the Brillouin zone. We suggest t hat this evolution is intimately related to the evolution of the antif erromagnetic (AF) order with doping.