International Journal of Modern Physics B

Superconducting phases in a generalized Hubbard chain with additional off-diagonal hopping processes

Hanqin Ding, Jun Zhang

Published Dec 15, 2016• 0 citations

Abstract

Applying the bosonization and renormalization group techniques, we study a generalized Hubbard chain incorporating extra off-diagonal hopping processes in the weak regime, and determine rich ground-state phase diagrams. At half filling, in addition to the insulating phases (HI, MI and DI), there exist the superconducting phases (LE and LL). The off-diagonal hopping accounts for the occurrence of insulator–superconductor transition. Away from half filling, the transition from the LL to LE phase takes place, and the insulating phases disappear. The result provides an insignificant insight into unconventional scenarios for Cooper pairing and insulator-superconductor transition.

DOI: 10.1142/s0217979217500588

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International Journal of Modern Physics B

Superconducting phases in a generalized Hubbard chain with additional off-diagonal hopping processes

Hanqin Ding, Jun Zhang

Published Dec 15, 2016• 0 citations

Publisher

Abstract

DOI: 10.1142/s0217979217500588

Related papers

η -pairing superconductivity in the Hubbard chain with pair hopping

G. I. Japaridze, A. P. Kampf, Michael Sekania +2 more

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Phase diagram of the half-filled Hubbard chain with next-nearest-neighbor hopping

S. Daul, R. M. Noack

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arXiv:cond-mat/9907256Physical review. B, Condensed matterJan 15, 200053 citations

t

equals the correlated hopping integral

X.

The phase diagram for the strongly correlated state with only singly occupied sites, the weakly correlated state, where single and double occupation is allowed, and for the superconducting state, was determined for any value of

X

and any electron concentration

n.

At the half-filled band

(n=1)

a direct transition from the superconductor to the Mott insulator was found. In the region of strong correlations the superconducting solution is stable for

n

close to 1, in contrast to the case of weak correlations, in which superconductivity occurs at $n\ensuremath{\approx}0$ and $n\ensuremath{\approx}2.$ We have also found that strong correlations change the characteristics of the superconducting phase, e.g., the gap in the excitation spectrum exhibits a nonexponential dependence on the on-site Coulomb integral

U

close to the phase-transition point.

(U \leq 2t)

, while the system is shown to become insulating for yet larger

U>U_C\sim 3t

from a direct evaluation of the charge gap with the density-matrix renormalization group method. The results are consistent with Fabrizio's recent weak-coupling theory which suggests a transition from a superconductor into an insulator at a finite U.

{t}_{2}

leads to a band structure with four Fermi points rather than two, producing a spin-gapped metallic phase. As U is increased in this regime, the system undergoes a Mott-Hubbard transition to a frustrated antiferromagnetic insulator.