Electronic structure of the CuO 2-plane of cuprate superconductors

Abstract

Electronic band structure of the CuO 2-plane common to cuprate superconductors is calculated with a novel approach, assuming that the plane consists of CuO 6- 4 and Cu 2+ ions. Cluster orbitals of a CuO 6- 4 ion are calculated with ab initio UHF SCF MO method. In the CuO 2-plane, the highest occupied MO (HOMO) is antibonding combination of π type O(2p x,y ) orbitals. The energy band structure is calculated by tight binding approximation with each MOs. Mid-infrared exciton bands of the doped CuO 2 plane are explained as interband transitions to the π holes of O(2p x,y ) antibonding type HOMO band from the degenerate O(2p x ) and O(2p y ) type next HOMO bands.