Doping dependence of chiral superconductivity in near 45 twisted bilayer cuprates

We study a one -band Hubbard model for a twisted cuprate bilayer with a twist angle of 43.6 degrees and a moire cell containing 58 sites. We use the variational cluster approximation (VCA), which treats short-range correlations exactly and leads, in single layers, to a dome of d -wave superconductivity away from half filling from strong on -site repulsion alone. We find a time -reversal -symmetry (TRS) breaking phase in a small doping interval in the overdoped region when interlayer tunneling is strong enough. Contrary to expectations, being closer to the 45 degrees twist angle does not expand this TRS region compared to a previous study [Lu and Senechal, Phys. Rev. B 105, 245127 (2022)] on a 53 degrees twist angle. This is attributed to the fact that the two superconducting states in competition have almost identical nodal structures.