Feshbach resonances of doped holes in an antiferromagnet

Feshbach resonances between neutral atoms are a powerful tool in modern ultracold atom experiments because they mediate strong interactions between otherwise only weakly interacting objects. Here, we extend the idea of Feshbach resonances to the low-energy emergent quasiparticles of a strongly correlated background. We argue that dopants in the antiferromagnetic, Mott insulating phase of the Fermi-Hubbard model form a well-defined multi-channel model. This allows us to show that the interaction is dominated by two channels yielding d-wave scattering between magnetic polarons, which we derive ab initio from geometric string theory in the t-J model. In the low doping regime, the effective interactions result in a d-wave BCS superconductor of magnetic polarons. This constitutes a new type of pairing mechanism, which potentially plays an important role for high-Tc superconductivity in cuprates.