η-pairing superconductivity in the Hubbard chain with pair hopping

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-η0 phase) and Q = π (ηπ-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-η0 and ηπ phases and the metallic Luttingerliquid phase. The BCS-η0 phase exhibits smooth crossover from a weak-coupling BCS type to a strong coupling local-pair regime. The ηπ phase shows properties of the doublon (zero size Cooper pair) superconductor with Cooper pair center-of-mass momentum Q = π. The transition into the ηπ-paired state corresponds to an abrupt change in the groundstate structure. After the transition the conduction band is completely destroyed and a new ηπ-pair band corresponding to the strongly correlated doublon motion is created.

Superconductivity, Charge Orderings, Magnetism, and Their Phase Separations in the Ground State of Lattice Models of Superconductor with Very Short Coherence Length

“…lattices, which consist of two interpenetrating lattices). In the presence of finite single electron hopping t = 0, both of the above-mentioned symmetries are broken in the general case [18][19][20][21][22][23][24][25][26][27][28][29][30], but the detailed discussion of effects of t = 0 is beyond the scope of this publication. Moreover, because of the particle-hole symmetry of model (1) the phase diagrams obtained are symmetric with respect toμ = 0 (μ = μ − U/2 − W 0 , W 0 = zW ) as well as n = 1.…”

Superconductivity of repulsive particles

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Ground State Phase Diagram of the Extended Hubbard Model with Pair-Hopping Interaction in the Limit of Very Narrow Bandwidth

“…On the diagrams three homogeneous phases occur: superconducting (SS for J > 0 is not considered in this paper. It is because negative U stabilizes superconducting phases for any n and only the SC phases occur for U < 0 (and: |U | D or |J| D) [1,5,[7][8][9][10][11][12]. The magnetic (MG) phases (F or AF) are stabilized by large enough U/|J|, whereas large |J|/U favours the SC phases (SS or ηS depending on the sign of J).…”