Fig. 1: 4e-SC from fluctuating PDW.

a The effective pairing interaction for PDW bosons via exchanging fermions. Here ± Q and ± P are related by consecutive π/2 rotations. When Eq. (1) is satisfied, the internal fermions are on the Fermi surface. b Continuum model for PDW with O(2) symmetry from ref. ⁴⁹. The orange area is the filled Fermi sea, and the PDW momentum Q takes values on the Bose surface represented by the red circle. The model can be continuously tuned such that \(| {\boldsymbol{Q}}| =\sqrt{2}{k}_{F}\). c The PDW model realized on a square lattice when the fermions relevant for pairing are close to the Van Hove points (0, π) and (π, 0) and the PDW momentum is close to (π, π). d PDW flucutations in the spin-fermion model^42,44. The four hot spots (black dots) near (π, 0) form a square, and the momenta for the potential PDW orders also form a square. The models in c and d satisfy the condition in Eq. (1).