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Session Q11 - HTSC: PHOTOEMISSION
Mixed session, Friday morning, March 24, 8:00
Room B3, San Jose Convention Center
The possible presence of surface states (SS's) has substantial implications for the interpretation of angle-resolved-photoemission spectra (ARPES) in the high-Tc's. SS's would complicate the mapping of the bulk bands and Fermi surfaces, and make it more difficult to determine the size and symmetry of the superconducting order parameter via the ARPES, bearing thus on the issue of mechanism of superconductivity. In this connection we have generalized and implemented the one-step methodology for obtaining angle-resolved photo-intensities in order to treat arbitrarily complex lattices[A. Bansil et al., J. Phys. Chem. Solids 54, 1185(1993); K. Gofron et al., Phys. Rev. Letters 73 (1994)]. Our first-principles computations of ARPES spectra predict the existence of SS's on the (001)-surface of Nd-Ce-Cu-O. Two Shockley-type surface state bands in the vicinity of the Fermi energy are identified. The associated states possess quite different characteristics in terms of their binding energies, dispersion with k_\Vert , and the polarization and photon energy dependence of the spectral peaks. Although our theoretical predictions are consistent with the available ARPES data, further high-resolution photoemission as well as inverse photoemission measurements from well characterized surfaces of Nd-Ce-Cu-O would be valuable. Work supported in part by DOE, NSF, and Academy of Finland.