Chemical and structural effects on the electronic states of (Hg, Tl, Pb, Bi)-based cuprate superconductors

The electronic energy bands have been calculated for the new single-layer and triple-layer Hg-based superconductors, HgBa₂CuO₄ and HgBa₂Ca₂Cu₃O_y, for the analogous Tl-and Bi-based materials, and for hypothetical Pb-based materials. As one moves across the last row of the periodic table, from Hg to Bi,s- andp-derived bands pass below the Fermi energy, to influence hole doping of the copper oxide planes and transport in the other layers of the material. The dispersion of these bands is significantly affected by the crystal structure. The calculations were performed with a simple chemical model.