Role of site selectivity, dimensionality, and strong correlations in angle-resolved photoemission from cuprate superconductors

We have carried out extensive first-principles computations of angle-resolved photoemission ( ARPES) spectra from the cuprate superconductors within the general framework of the local density approximation ( LDA). Selected results on Bi2Sr2CaCu2O8 ( Bi2212), La2- x Sr-x CuO4 ( LSCO) and Nd2-x Ce-x CuO4 ( NCCO) are presented and discussed. Our focus is on understanding how the underlying electronic structure is mapped via the complex process of photoexcitation into the observed ARPES intensities. Effects of the ARPES matrix element and its remarkable selectivity properties with respect to the energy and polarization of the incident photons in exciting a specific state and/or electrons from a particular site in the lattice are clarified. The importance of deviations from perfect two-dimensionality and the associated interlayer couplings in shaping the ARPES spectra of the cuprates is delineated. Our computations explain many salient features of the experimental spectra. Surprisingly, this agreement extends in some cases to the underdoped regime where strong electron correlations are obviously important. We discuss how the LDA-inspired tight-binding parameters can serve as a useful starting point for the treatment of strong coupling effects in the cuprates.