Synthetic-gauge-field stabilization of the chiral-spin-liquid phase

Abstract

© 2016 American Physical Society. We explore the phase diagram of the SU(N) Hubbard models describing fermionic alkaline-earth-metal atoms in a square optical lattice with, on average, one atom per site, using a slave rotor mean-field approach. We find that the chiral spin liquid (CSL) predicted for N≥5 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 show that by adding a uniform artificial gauge field with 2π/N flux per plaquette, the CSL becomes the ground state for all N≥3 at intermediate interactions, persists to weaker interactions, and exhibits a larger spin gap. For N≥5 we find the CSL is the ground state everywhere the system is a Mott insulator. The gauge field stabilization of the CSL at lower interactions, and thus at weaker lattice depths, together with the increased spin gap, can relax the temperature constraints required for its experimental realization in ultracold atom systems.