Electronic structure and charge fluctuation in Bi₂Sr₂CuO₆

Abstract

Tight-binding band calculations were performed on Cu₂Bi₂O⁶⁻₈, Cu₄O¹⁶⁻₁₂ and Bi₄O⁴⁻₈ complexes modelling the Bi₂Sr₂CuO₆ sublattice, CuO₂ sheet and Bi-O double layer, respectively. We investigate the effect of the planar-oxygen breathing-mode vibration on the dx²−y² valence band and Mulliken charge of Cu and O. The results show that the breathing mode causes splitting of the dx²−y² bands at E_f, and charge fluctuation between Cu-O complexes. The oxidation strengthens the charge fluctuation, thereby favouring the formation of the pairs.