Observation of generalized t-J spin dynamics with tunable dipolar interactions

Long-range and anisotropic dipolar interactions profoundly modify the dynamics of particles hopping in a periodic lattice potential. We report the realization of a generalized t-J model with dipolar interactions using a system of ultracold fermionic molecules with spin encoded in the two lowest rotational states. We independently tuned the dipolar Ising and spin-exchange couplings and the molecular motion and studied their interplay on coherent spin dynamics. Using Ramsey spectroscopy, we observed and modeled interaction-driven contrast decay that depends strongly both on the strength of the anisotropy between Ising and spin-exchange couplings and on motion. This study paves the way for future exploration of kinetic spin dynamics and quantum magnetism with highly tunable molecular platforms in regimes that are challenging for existing numerical and analytical methods. The so-called t-J model describes the dynamics of interacting particles on a lattice. Although this model has been studied extensively using numerical methods, realizing it in a quantum simulation experiment with tunable parameters is challenging. Carroll et al. used a system of fermionic potassium-rubidium molecules residing in an optical lattice to simulate a generalized t-J model based on dipolar interactions. The researchers explored the system’s out-of-equilibrium dynamics using spectroscopic techniques. —Jelena Stajic