Mean Field Study of Superconductivity in the Square Lattice $t$-$J$ Model with Three-Site Hopping

TL;DR

This study uses mean-field theory to show that including three-site hopping in the $t$-$J$ model suppresses $d$-wave superconductivity, providing insight into differences observed between Hubbard and $t$-$J$ models in cuprates.

Contribution

It reveals the suppressive effect of three-site hopping on $d$-wave superconductivity in the $t$-$J$ model, clarifying discrepancies with the Hubbard model.

Findings

Three-site hopping suppresses $d$-wave superconductivity.

Competition between superexchange and three-site hopping influences pairing symmetry.

Results align with numerical studies showing weak or absent superconductivity in the Hubbard model.

Abstract

It remains an open question whether the two-dimensional single-band pure Hubbard model and its related pure $t$-$J$ model truly capture the superconducting order in cuprates. Recent numerical studies on this issue have raised a notable disparity in superconducting order between the pure Hubbard model and the pure $t$-$J$ model. Inspired by these, we investigate the role of the three-site hopping term in $d$-wave superconductivity, such a term is usually neglected in the effective Hamiltonian of the Hubbard model, though its amplitude is of the same order as the superexchange coupling $J$ in the $t$-$J$ model. Our slave-boson mean-field solution demonstrates the suppression of $d$-wave superconducting order by incorporating the three-site hopping term, consistent with numerical observations by the density matrix renormalization group. This suppression could be understood as a result of competition between superexchange interaction and three-site hopping, the former favors $d$-wave pairing while the latter favors $s$-wave pairing. We also discussed its role in quasiparticle dispersion and boson-condensation temperature. Our findings may offer an alternative understanding of the recent numerical contrasting findings in the strong coupling regime: the absent or weak superconductivity in the pure Hubbard model, while the robust superconductivity in the $t$-$J$ model without including the three-site hopping term.