THE ELECTRON SPECTRUM OF THE HUBBARD-MODEL WITH COUPLING TO PSEUDOSPIN DEGREES OF FREEDOM

The model Hamiltonian describes the anharmonic vibrations of the apex oxygen atoms (O(4)) in YBaCuO-type superconductors by adding pseudospi n degrees of freedom to the local part of a Hubbard Hamiltonian. The s ingle-electron spectrum of this model is calculated self-consistently using a Green's function technique. We find additional subbands as a r esult of the added interaction accompanied by a destruction of electro n-hole symmetry. Moreover, the system can develop hole conductivity at half filling which could be important for high temperature supercondu ctivity in such materials.