We investigate the interplay of phonons and correlations in superconducting pairing by introducing a model Hamiltonian with on-site repulsion and couplings to several vibration branches having the Cu-O plane of the cuprates as a paradigm. We express the electron-phonon coupling (EP) through two force constants for O-Cu and O-O bond stretchings. Without phonons, this reduces to the Hubbard Model, and allows purely electronic W=0 pairing. A W=0 pair is a two-body singlet eigenstate of the Hubbard Hamiltonian, with no double occupancy, which gets bound from interactions with background particles. Indeed, this mechanism produces a Kohn-Luttinger-like pairing from the Hubbard repulsion, provided that its symmetry is not severely distorted. From the many-body theory, a canonical transformation extracts the effective two-body problem, which lends itself to numerical analysis in case studies. As a test, we use as a prototype system the $\cu$ cluster. We show analytically that at weak EP coupling the additive contributions of the half-breathing modes reinforce the electronic pairing. At intermediate and strong EP coupling and $U \sim t$ , the model behaves in a complex and intriguing way.We investigate the interplay of phonons and correlations in superconducting pairing by introducing a model Hamiltonian with on-site repulsion and couplings to several vibration branches having the Cu-O plane of the cuprates as a paradigm. We express the electron-phonon coupling (EP) through two force constants for O-Cu and O-O bond stretchings. Without phonons, this reduces to the Hubbard Model, and allows purely electronic W=0 pairing. A W=0 pair is a two-body singlet eigenstate of the Hubbard Hamiltonian, with no double occupancy, which gets bound from interactions with background particles. Indeed, this mechanism produces a Kohn-Luttinger-like pairing from the Hubbard repulsion, provided that its symmetry is not severely distorted. From the many-body theory, a canonical transformation extracts the effective two-body problem, which lends itself to numerical analysis in case studies. As a test, we use as a prototype system the $\cu$ cluster. We show analytically that at weak EP coupling the additive contributions of the half-breathing modes reinforce the electronic pairing. At intermediate and strong EP coupling and $U \sim t$, the model behaves in a complex and intriguing way.

arXiv:cond-mat/0406220Journal of Physics Condensed MatterJul 2, 20041 citation

Repulsive bound-electron pairs in a Peierls lattice

Uriel Alberto Díaz-Reynoso, Ernesto Huipe-Domratcheva, Oracio Navarro

A new class of repulsive bound-electron pairs have been found in a Peierls lattice within the Hubbard model for energies E < 0 despite U > 0. These new repulsive bound-electron pairs have a high degree of localization as both the correlation energy U and the tS/tL hopping ratio increases. In order to study electronic correlation in Peierls lattices, our previous real space mapping method has also been extended to the so called generalized mapping method which is briefly presented here. In this paper, we concentrate our attention to discuss in detail the two-particle problem within a repulsive Hubbard model for the one-dimensional Peierls lattice.A new class of repulsive bound-electron pairs have been found in a Peierls lattice within the Hubbard model for energies E < 0 despite U > 0. These new repulsive bound-electron pairs have a high degree of localization as both the correlation energy U and the tS/tL hopping ratio increases. In order to study electronic correlation in Peierls lattices, our previous real space mapping method has also been extended to the so called generalized mapping method which is briefly presented here. In this paper, we concentrate our attention to discuss in detail the two-particle problem within a repulsive Hubbard model for the one-dimensional Peierls lattice.

Revista Mexicana de FísicaSep 1, 20231 citation

Phase separation and electron pairing in repulsive Hubbard clusters

ARMEN N. KOCHARIAN, Gayanath Fernando, Tun Wang +2 more

Bulletin of the American Physical SocietyMar 8, 20070 citations

Novel pairing in the Hubbard model with confinement potential

Masahiko Machida, Susumu Yamada, Yoji Ohashi +1 more

Physica C SuperconductivityMay 17, 20062 citations

Low density electron pairs in the extended Hubbard model

Hua Lin, W.C. Lau, W.Y. Chen

Synthetic MetalsOct 1, 19970 citations

U \sim t

, the model behaves in a complex and intriguing way.