Floquet-Engineering of Feshbach Resonances in Ultracold Gases

Abstract: Scattering resonances are fundamental in science, spanning energy scales from stellar nuclear fusion to ultracold collisions. In ultracold quantum gases, magnetic Feshbach resonances have transformed quantum many-body research by enabling precise interaction control between atoms. Here, we demonstrate unprecedented control to engineer new Feshbach resonances at tunable positions via Floquet driving in a $^{6}$Li atom gas, achieved through strong magnetic field modulation at MHz frequencies. This periodic modulation creates new resonances whenever dressed molecular levels cross the atomic threshold. By adding a second modulation at twice the base frequency, we tune the asymmetry of resonance loss profiles and suppress two-body losses from Floquet heating. This technique enhances control over atomic interactions, expanding possibilities for quantum simulations of complex systems and studies of exotic quantum phases.