Feshbach hypothesis of high-Tc superconductivity in cuprates

Resonant interactions associated with the emergence of a bound state constitute one of the cornerstones of modern many-body physics. Here, we perform theoretical analysis of interactions between charge carriers in doped Mott insulators and we find strong evidence of Feshbach resonance type interactions in the d_{x^2-y^2} channel that can support strong pairing. Here we argue that this paradigm possibly extends to Feshbach resonances between the low-energy emergent constituents in a class of strongly correlated high-temperature superconductors. We perform theoretical analysis of interactions between charge carriers in doped Mott insulators, modelled by a near-resonant two-channel scattering problem, and find strong theoretical evidence for Feshbach-type interactions in the $d_{x^2-y^2}$ channel that can support strong pairing, consistent with the established phenomenology of cuprates. Existing experimental and numerical results on hole-doped cuprates lead us to conjecture the existence of a long-lived, low-energy excited state of two holes with bipolaron character in these systems, which enables near-resonant interactions and can thus provide a microscopic foundation for theories of high-temperature superconductivity involving strong attraction, as assumed e.g. in BEC-BCS crossover scenarios. The emergent Feshbach resonance we propose could also underlie superconductivity in other doped antiferromagnets, as recently proposed for bilayer nickelates, highlighting its potential as a unifying strong-coupling pairing mechanism rooted in quantum magnetism.