Spin Fluctuations and High-Temperature Superconductivity in Cuprates

Abstract

A microscopic theory of spin excitations and superconductivity in strongly correlated electronic systems as cuprates is discussed. We argue that in the Mott-Hubbard regime with two Hubbard subbands, there emerges a new energy scale induced by kinematical interaction of electrons with spin fluctuations of the order of electronic kinetic energy. The spectrum of magnetic excitations reveals a small damping caused by the involvement of spin excitations in the decay process besides the particle-hole continuum. This results in the magnetic resonance mode (RM) with weak temperature dependence as observed in experiments. Electronic spectrum and superconductivity are studied within the extended Hubbard model which includes intersite Coulomb repulsion and electron-phonon interaction. We found the d-wave pairing with high- T c mediated by strong kinematical interaction of electrons with spin fluctuations. Contributions to the d-wave pairing coming from intersite Coulomb repulsion and phonons turned out to be small.