BAND MAPPING OF THE MODEL INSULATOR SR2CUO2CL2 - DISPERSION OF A SINGLE HOLE IN AN ANTIFERROMAGNETIC BACKGROUND

We report angle resolved photoemission measurements on Sr2CuO2Cl2, an insulating layered copper oxide. We map the energy-momentum dispersion of the highest energy band. We find that the width of this band is co nsistent with calculations based on variations of the Hubbard model. T he dispersion in model some directions and the position of the valence band maximum at (pi/2, pi/2) match predictions of the t-J model. Howe ver the overall shape of the band differs from these predictions. A co mparison of our data with spectra previously reported on metallic samp les leads to surprising new suggestions for the phenomenology of dopin g.