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تسجيل مستخدم جديدeta-superconductivity in the Hubbard chain with pair hopping
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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-eta_0 phase) and Q=pi (eta_pi-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-eta_0 and eta_pi phases and the metallic Luttinger-liquid phase. The BCS-eta_0 phase exhibits smooth crossover from a weak-coupling BCS type to a strong coupling local-pair regime. The eta_pi phase shows properties of the doublon (zero size Cooper pair) superconductor with Cooper pair center-of-mass momentum Q=pi. The transition into the eta_pi- paired state corresponds to an abrupt change in the groundstate structure. After the transition the conduction band is completely destroyed and a new eta_pi-pair band corresponding to the strongly correlated doublon motion is created.
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