Electronic structure of a step on cleaved surfaces of layered copper oxides

Abstract

The electronic structure of a step on cleaved surfaces of layered copper oxides is studied in terms of the Green function method. It is shown that if the edges of the steps are formed by Cu atoms, then deep electronic states appear in the forbidden gap preferably as a result of the breaking of Cu-O chemical bonds. On the other hand, if the boundary atoms are represented by 0 atoms, the above phenomenon is due to a change (rise) of the potential at the «surface» atoms. The rilling of the bands of these states with electrons may give rise to the one-dimensional surface conductivity. At low electron concentration in the bands, one has to expect a restructuring or the appearance of superconductivity properties in view of the fact that the fermi level approaches the van Hove singularity