Unconventional Superconducting States in the \(t-J\) Model on Creutz Lattice

We study the onset of unconventional pair superfluidity in the t-J model on the Creutz lattice, which shows strictly flat bands in the noninteracting regime, using renormalized mean-field theory. Our study reveals the competition and coexistence between intrachain electron pairs and interchain electron pairs with varying antiferromagnetic interaction strengths at zero temperature. We observe that interchain pairs persist under strong interchain antiferromagnetic interaction but are suppressed by intrachain antiferromagnetic interaction. Interestingly, as hole-doping increases, we find that intrachain and interchain pairs exhibit distinct properties: The interchain pairs display a dome-like shape reminiscent of the superconducting dome observed in high-\(T_{c}\) superconductors. In contrast, the intrachain pairs’ gap increases smoothly with the hole-doping level. Furthermore, we find that the interchain pairs are more robust than intrachain pairs under thermal fluctuations; their critical temperature is higher than that of intrachain pairs. It is implementable to simulate and control strong electron correlation behavior on the Creutz lattice in ultracold atoms experiment or other artificial structures. Our predictions are verifiable and promote the understanding of flat band superconductivity.