Competing s-wave pairing in overdoped t-J model

The d-wave pairing symmetry has long been considered a defining feature of high-temperature superconductivity in cuprates. In this work, we reveal that s-wave pairing states exhibit variational energies comparable to the d-wave state in a square t-J model, particularly at high doping levels (> 15%) by using the state-of-the-art tensor network simulation. This surprising result suggests that s-wave pairing may play an important role in the cuprate phase diagram, especially for the overdoped region. Our findings provide a potential resolution to discrepancies in recent Josephson tunneling experiments on twisted bilayer cuprates and offer new insights into the evolution of pairing symmetry with doping.