Superconductivity with and without glue and the role of the double-occupancy forbidding constraint in the t-J-V model

TL;DR

This paper investigates how the non-double-occupancy constraint affects superconductivity in the t-J-V model, revealing that it screens Coulomb repulsion and stabilizes d-wave pairing, with implications for understanding pairing mechanisms in cuprates.

Contribution

It demonstrates that considering the non-double-occupancy constraint and its fluctuations significantly alters the impact of Coulomb interactions on superconductivity in the t-J-V model.

Findings

Non-double-occupancy constraint screens Coulomb repulsion.

Superconductivity remains robust when fluctuations are included.

Unretarded pairing from spin-exchange interaction J is supported.

Abstract

The occurrence of retarded (with glue) and unretarded (without glue) pairing is thoroughly discussed in cuprates. We analyze some aspects of this problem in the context of the t-J-V model in a large-N approximation. When 1/N renormalizations are neglected the mean-field result is recovered, where the unretarded d-wave superconducting pairing triggered by the spin-exchange interaction J is obtained. However, the presence of a non-negligible nearest-neighbors Coulomb interaction V(q) kills superconductivity. If the non-double-occupancy constraint and its fluctuations are considered, the situation changes drastically. In this case, V(q) is screened making d-wave superconductivity very robust. In addition, we show that the early proposal for the presence of an unretarded pairing contribution triggered by the spin-exchange interaction J can be discussed in this context.