Mott transition and antiferromagnetism of cold fermions in the decorated honeycomb lattice

We investigate two-component ultracold fermions loaded in a decorated honeycomb lattice described by the Hubbard model with repulsive interactions and nearest-neighbor hopping. The phase transitions are studied by combining the cellular dynamical mean-field theory with the continuous-time quantum Monte Carlo method. For weak interactions, the quadratic band crossing point is broken to a linear band crossing point and the system becomes a semimetal. With increasing interaction, the system undergoes a first-order phase transition to an antiferromagnetic Mott insulator at low temperatures. Below the critical temperature, due to the charge nematic fluctuation, a nematic metal forms between the semimetal and the antiferromagnetic Mott insulator. The effects of lattice anisotropy are also addressed. Furthermore, we discuss how to detect these phases in real experiments.