Floquet engineering of Feshbach resonances in ultracold gases

Scattering resonances are fundamental to many areas of physics, occurring across a wide range of energy scales. 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 Feshbach resonances at tunable positions via Floquet driving in a lithium-6 (^{6}Li) atom gas, achieved through strong magnetic field modulation at megacycles per second frequencies. This periodic modulation creates scattering 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.