Spin-polaron theory of high-(Tc) superconductivity: 2, electronic structure of the CuO(sub 2) planes

摘要

After an introductory discussion of electronic structure calculations for the CuO(sub 2) planes in the copper-oxide based high-(Tc) superconductors, the method suggested by Slater for studying antiferromagnetic (AF) metals is described. In this method, as applied here, the chemical unit cell is doubled to form a magnetic unit cell which contains one Cu ion with predominantly up spin and one with predominantly down spin. Down spins are kept off up-spin sites, and conversely, by the introduction of a Hubbard U term. As a result, the band structure obtained is typical of that for a Mott-Hubbard (M-H) or, more generally, a charge transfer insulator. Conductivity in the a-b plane results when holes are introduced into the M-H valence band. The band structure as a function of the parameters in Koster-Slater type calculations is discussed and the Fermi surface is described. A calculation of the delocalization energy for spin-polaron formation is carried out within the context of the band calculations.