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η-superconductivity in the Hubbard chain with pair hopping

G. I. Japaridze·A. P. Kampf·M. Sekania·P. Kakashvili·Ph. Brune
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Abstract

The ground state phase diagram of the 1D Hubbard chain with pair-hopping interaction is studied. The analysis of the model is performed using the continuum-limit field theory approach and exact diagonalization studies. At half-filling the phase diagram is shown to consist of two superconducting states with Cooper pair center-of-mass momentum Q=0 (BCS-η_0 phase) and Q=π(η_π-phase) and four insulating phases corresponding to the Mott antiferromagnet, the Peierls dimerized phase, the charge-density-wave (CDW) insulator as well as an unconventional insulating phase characterized by the coexistence of a CDW and a bond-located staggered magnetization. Away from half-filling the phase diagram consists of the superconducting BCS-η_0 and η_πphases and the metallic Luttinger-liquid phase. The BCS-η_0 phase exhibits smooth crossover from a weak-coupling BCS type to a strong coupling local-pair regime. The η_πphase shows properties of the doublon (zero size Cooper pair) superconductor with Cooper pair center-of-mass momentum Q=π. The transition into the η_π- paired state corresponds to an abrupt change in the groundstate structure. After the transition the conduction band is completely destroyed and a new η_π-pair band corresponding to the strongly correlated doublon motion is created.

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G. I. Japaridze, A. P. Kampf, M. Sekania, P. Kakashvili, Ph. Brune. 2000-06-26. η-superconductivity in the Hubbard chain with pair hopping. https://doi.org/10.1103/physrevb.65.014518

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