POLARIZATION-DEPENDENT PHOTOEMISSION-STUDIES OF THE ELECTRONIC-STRUCTURE OF LA2CUO4-CRYSTALS(X SINGLE)

Recently we have reported the first resonance photoemission results on cleaved single crystal superconductor La2CuO4+x using excitation ener gies below 20 eV at a temperature of about 30 K [1]. Spectral enhancem ent of the valence region of 6 eV binding energy (BE) at photon energi es around 17 eV were found to be consistent with autoionization resona nce excitations. We now present new polarization-dependent angle-resol ved UPS results on the resonances. Two distinct features of different symmetry character are resolved and they resonate with similar intensi ty. The atomic origin of the resonances is discussed and our findings impose some important questions which band structure calculations for high temperature superconductors will have to address.