The Role of In-plane Oxygens in Optimally Doped NCCO
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Within the framework of the three-band Hubbard (Emery) model of high-temperature superconductors, we find a new physical regime for the electron-doped compound NCCO at optimal doping. It is characterized by a strong renormalization of the bare copper–oxygen hopping, similar to the one on the hole-doped side, and a low value of the effective copper–oxygen splitting. After a zeroth order fit of the Fermi surface is achieved, ARPES data are reproduced by adding a simple phenomenological weak-coupling antiferromagnetic perturbation of the conduction electrons. The experimental situation corresponds to a pseudogap across the whole Fermi surface. The wide dispersive features in NCCO ARPES spectra are analogous to the hump in BSCCO. The oxygen degree of freedom dominates the band structure of both NCCO and BSCCO, however, in NCCO this cannot be demonstrated without simultaneously accounting for the antiferromagnetic scattering. The difference in T c of the two compounds may be related in part to the difference in the calculated densities of states.
KeywordsEmery model Magnetic fluctuations Electron-doped superconductors
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