Resonant pair-exchange scattering and BCS-BEC crossover in a system composed of dispersive and heavy incipient bands: A Feshbach analogy

We theoretically show that a two-band system with very different masses harbors a resonant pair scattering that leads to novel pairing properties, as highlighted by the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensation (BEC) crossover. Most importantly, the interband pair-exchange coupling induces an effective intraband attraction in each band, enhancing the superfluidity/superconductivity. The effect, a kind of Suhl-Kondo mechanism, is specifically enhanced when the second band has a heavy mass and is incipient (lying close to, but just above, the chemical potential mu), which we call a resonant pair scattering. By elucidating the dependence of the effective interactions and gap functions on mu, we can draw an analogy between the resonant pair scattering and the Feshbach resonance.

Automated summary

This study theoretically demonstrates the existence of resonant pair scattering in a two-band system with significantly different masses, leading to novel pairing properties and enhancing superfluidity/superconductivity.