High-resolution angle-resolved photoemission study of bulk electronic states in YBa₂ Cu₃ O_{7 - δ}

We have studied low-energy electronic structure of YBa₂ Cu₃ O_{7 - δ} using high-resolution angle-resolved photoemission spectroscopy (ARPES). By carefully tuning photon energy and polarization of incident light, we identified five different bands in the vicinity of the Fermi level, those are surface-bilayer-derived bonding and antibonding bands, their bulk counterparts, and CuO-chain-derived band, respectively. The surface bands show metallic property reflecting highly overdoped character, while bulk bands show signature of a d_{x2 - y2}-wave superconducting gap opening. The present ARPES result suggests the universality of the bulk electronic states in bilayer high-T_c superconductors.