Electronic band properties and superconductivity in La2−yXyCuO4

Abstract

The results of electronic-structure calculations for tetragonal ${\mathrm{La}}_2$ ${\mathrm{CuO}}_4$ provide insight concerning the origin of high-temperature superconductivity in the ${\mathrm{La}}_{2\mathrm{-}\mathrm{y}}$ ${\mathrm{X}}_{\mathrm{y}}$ ${\mathrm{CuO}}_4$ alloys. A half-filled Cu(3d)-O(2p) band with two-dimensional character and a nearly square Fermi surface produces a Peierls instability for y=0 that opens a semiconductor gap over the Fermi surface. Alloying with divalent or tetravalent atoms should spoil the nesting features while maintaining the strong coupling of O phonons to the conduction electrons.