Synthetic gauge fields stabilize a chiral spin liquid phase

Abstract

We calculate the phase diagram of the SU($N$) Hubbard model describing fermionic alkaline earth atoms in a square optical lattice with on-average one atom per site, using a slave-rotor mean-field approximation. We find that the chiral spin liquid predicted for $N\ge5$ and large interactions passes through a fractionalized state with a spinon Fermi surface as interactions are decreased before transitioning to a weakly interacting metal. We also show that by adding an artificial uniform magnetic field with flux per plaquette $2\pi/N$, the chiral spin liquid becomes the ground state for all $N\ge 3$ at large interactions, persists to weaker interactions, and its spin gap increases, suggesting that the spin liquid physics will persist to higher temperatures. We discuss potential methods to realize the artificial gauge fields and detect the predicted phases.