Stable Algebraic Spin Liquid in a Hubbard Model
We show the existence of a stable algebraic spin liquid (ASL) phase in a Hubbard model defined on a honeycomb lattice with spin-dependent hopping that breaks time-reversal symmetry. The effective spin model is the Kitaev model for large on-site repulsion. The gaplessness of the emergent Majorana fermions is protected by the time-reversal invariance of this model. We prove that the effective spin model is time-reversal invariant in the entire Mott phase, thus ensuring the stability of the ASL. The model can be physically realized in cold atom systems, and we propose experimental signals of the ASL.