Off-Diagonal Coulomb Interactions in the Extended Peierls-Hubbard Model: Exact Diagonalization Results

Abstract

As evidenced by the many contributions to these proceedings, the role of electron-electron interactions in solid-state systems continues to be the subject of intense investigation and debate. Much of the recent discussion has been stimulated by experimental work on exciting novel materials, including high-temperature superconducting copper oxides, “heavy-fermion” systems, organic synthetic metals, and halogen-bridged transition-metal chains. Unlike conventional metals, for which standard single-electron (band) theories describe quantitatively the electronic structures and excitations, these new materials are currently thought to have properties dominated by many-body effects arising from strong electron-electron interactions. It is essential to have tractable models that capture the essence of both electron-phonon (e-p) and electron-electron (e-e) interactions and that represent faithfully their synergetic, or competing, effects.