Strongly-correlated superconductivity with spin-orbit coupling

Motivated by the recent discovery of a field-mediated parity switch within the superconducting state of CeRh2As2 [Khim et al., Science 373, 1012 (2021)], we investigate the superconducting phase diagram of a strongly-coupled Rashba mono- and bilayer. Our model extends the usual two-dimensional Hubbard model by including Rashba spin-orbit coupling due to broken inversion symmetry, and interlayer hopping in the case of the bilayer. The strong correlations due to the on-site repulsion are accounted for within the auxiliary boson mean-field theory.

We find that the usual d-wave solution is replaced by an extended s-wave state at sufficiently large interlayer hopping or spin-orbit coupling strength. Including an applied magnetic field we observe a transition to an exotic "staggered singlet" odd-parity state, recalling the phase diagram of CeRh2As2.