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

TL;DR

This study investigates thermodynamic properties and short-range spin correlations of ultracold fermions in the honeycomb lattice, revealing stronger correlations and cooling effects compared to the square lattice, with implications for optical lattice experiments.

Contribution

It provides the first detailed comparison of thermodynamics and correlations between honeycomb and square lattices using advanced quantum Monte Carlo methods.

Findings

Nearest-neighbor spin correlations are stronger in the honeycomb lattice.

The honeycomb lattice exhibits a more pronounced anomalous double occupancy region.

Stronger adiabatic cooling is observed in the honeycomb lattice.

Abstract

We use determinantal quantum Monte Carlo simulations and numerical linked-cluster expansions to study thermodynamic properties and short-range spin correlations of fermions in the honeycomb lattice. We find that, at half filling and finite temperatures, nearest-neighbor spin correlations can be stronger in this lattice than in the square lattice, even in regimes where the ground state in the former is a semimetal or a spin liquid. The honeycomb lattice also exhibits a more pronounced anomalous region in the double occupancy that leads to stronger adiabatic cooling than in the square lattice. We discuss the implications of these findings for optical lattice experiments.