Observation of collapse and revival of atomic four-wave mixing in Bose gases

Atomic four-wave mixing (FWM) is an important nonlinear process in ultracold physics. Despite numerous works on atomic FWM, the phase coherence effect has not been extensively studied. Here, by preparing multiple spin-momentum modes with ultracold ⁸⁷Rb atoms in a crossed dipole trap and applying an external magnetic field to regulate the atomic motions and interactions, we extensively investigate how the coherence fluctuation affects the atomic FWM process. We observe that the atomic motion and spin-exchange collision involve a periodic collapse and revival of the yield fraction of the atomic FWM. The oscillation period is mainly determined by the spin-exchange rate and thus the atomic scattering cross section. Our work demonstrates that atomic FWM can be used to probe the coherence and the atomic interactions, which should benefit various areas related to multicomponent atomic interactions and spin dynamics in the future.