Short-Range Correlations and Cooling of Ultracold Fermions in the Honeycomb Lattice

We study experimentally relevant thermodynamic properties and spin correlations of the Hubbard model in the honeycomb lattice by using determinantal quantum Monte Carlo simulations and numerical linked-cluster expansions. We find that the honeycomb lattice exhibits a more pronounced anomalous region in the double occupancy that leads to stronger adiabatic cooling than in the square lattice. We also find that, at half filling and finite temperature, nearest-neighbor spin correlations can be stronger in the honeycomb lattice than in the square lattice, even in regimes where the ground state in the former is a semimetal or a spin liquid while it is an antriferromagnetic Mott insulator in the latter. The implications of these findings for optical experiments are also discussed.