Matrix element and strong electron correlation effects in ARPES from cuprates

We discuss selected results from our recent work concerning the angle-resolved photoemission (ARPES) spectra from the cuprates. Our focus is on developing an understanding of the effects of the ARPES matrix element and those of strong electron correlations in analyzing photointensities. With simulations on Bi2Sr2CaCu2O8+delta (Bi2212), we show that the ARPES matrix element possesses remarkable selectivity properties. such that by tuning the photon energy and polarization, emission from the bonding or the antibonding states can be enhanced. Moreover, at low photon energies (below 25 eV), the Fermi surface (FS) emission is dominated by transitions from just the O-atoms in the CuO2 planes. In connection with strong correlation effects, we consider the evolution with doping of the FS of Nd2-xCexCuO4+/-delta (NCCO) in terms of the t - t' - U Hubbard model Hamiltonian. We thus delineate how the FS evolves on electron doping from the insulating state in NCCO. The Mott pseudogap is found to collapse around optimal doping suggesting the existence of an associated quantum critical point. (C) 2004 Elsevier Ltd. All rights reserved.