Site-selectivity properties of the angle-resolved photoemission matrix element in Bi2Sr2CaCu2O8 -: art. no. 054522

We show that the angle-resolved photoemission (ARPES) spectra for emission from the bonding as well as the antibonding Fermi-surface sheet in Bi2Sr2CaCu2O8 possess remarkable site, selectivity properties, in that the emission for photon energies less than 25 eV is dominated by p-->d excitations from just the O sites in the CuO2 planes. There is little contribution from Cu electrons to the ARPES intensity, even though the initial states at the Fermi energy contain an admixture of Cu-d and O-p electrons. We analyze the origin of this effect by considering the nature of the associated dipole matrix element in detail and find that various possible transition channels (other than p-->d on O sites) are effectively blocked by the fact that the related radial cross section is small and/or a lack of available final states. Our prediction that ARPES can preferentially sample Cu or O states by tuning the photon energy suggests different possibilities for exploiting energy dependent ARPES spectra for probing initial state characters in the cuprates.