REDUCED PAIRING HAMILTONIAN FOR INTERATOMIC TWO-ELECTRON EXCHANGE IN LAYERED CUPRATES

Abstract

A detailed Linear Combination of Atomic Orbitals (LCAO) tight-binding model is developed for the layered High-Temperature Superconductor (HTSC) cuprates. The band structure of these materials is described using a σ-band Hamiltonian employing Cu 4s, Cu 3dx2 - y2, O 2px and O 2py atomic orbitals. The Fermi level and the shape of the resulting Fermi surface are fitted to recent Angle Resolved Photon Emission Spectroscopy (ARPES) data to realistically determine the dispersion in the conduction band. Electron-electron interactions and, ultimately, Cooper pairing are obtained by introducing a Heitler–London, two-electron exchange between adjacent orbitals within the CuO 2 plane. Finally, using the LCAO wavefunctions determined by the band structure fit, the Bardeen–Cooper–Schrieffer (BCS) type kernel is derived for interatomic exchange.