EFFECT OF POLARIZATION OF THE EXCITING-LIGHT ON RESONANT PHOTOELECTRON EMISSION FROM LA2CUO4-CRYSTALS(DELTA SINGLE)

A resonant increase in the emission from electron states with a bindin g energy almost-equal-to 6 eV an exciting-photon energy almost-equal-t o 17 eV has been observed in photoelectron spectra of the valence band of La2CuO4+delta single crystals. The intensity of the resonant-emiss ion peak is comparable to the maximum of the valence band. An effect o f the polarization of the exciting light on the nature of the resonanc e has been observed for the first time: As the orientation of the pola rization vector with respect to the crystallographic axes is varied, c hanges occur in the binding energy of the resonant peak and in the res onant emission frequency. The effect, with very slight differences, is observed for both insulating and superconducting samples. The experim ental data are discussed within the framework of the theory of resonan t photoemission. (C) 1994 American Institute of Physics.