BASAL-PLANE SURFACES OF YBA2CU3O7 - SINGLE-PARTICLE RESULTS AND VALENCE-BAND SPECTRA

YBa2Cu3O7 has a complex structure, which allows for six different basal-plane surfaces. For each of them we have calculated the local density of states in the outermost crystal layers using a tight-binding method, and found that surface states with dangling-bond character are present. The surfaces obtained by cutting the bond between in-plane copper ions and axial oxygen atoms appear to be electrostatically stable, the charge distribution in the outermost planes closely resembling the bulk one. Their surface band structures show dangling-bond states with significant dispersion, which are proposed to be responsible for the surface feature observed by angle-resolved photoemission. By using a model Hamiltonian that includes correlation effects, we have calculated the hole self-energy and determined the valence-band satellite distribution for different crystal terminations and compositions. The results show that satellites are significantly affected by the surface conditions. It is concluded that the role of the surface is crucial in modeling the photoemission spectra.