Pair breaking and Néel ordering in attractive three-component Dirac fermions

Abstract

We employ the determinant quantum Monte Carlo method to investigate finite-temperature properties of the half-filled attractive three-component Hubbard model on a honeycomb lattice. By adjusting the anistropy of interactions, the symmetry of the Hamiltonian changes from SU(3) to SU(2)⊗ U(1) and finally to SO(4)⊗ U(1). The system undergoes the phase transition between the disorder state and the charge density wave (CDW) state around the SU(3) symmetric points. Away from the SU(3) symmetric points and the SO(4)⊗ U(1) symmetric points, the system can enter into the color density wave (color DW) phase or the color selective density wave (CSDW) phase. Around the SO(4)⊗ U(1) symmetric points, the pairing order and the CSDW order can be both detected. The pairing order is quickly suppressed away from the SO(4)⊗ U(1) symmetric points because Cooper pairs are scattered. When the anisotropy of interaction exists, Néel order appears because the number of off-site trions |12, 3 is greater than the number of other two types of off-site trions and off-site trions |12, 3 do not distribute randomly. The calculated entropy-temperature relations show the anisotropy of interactions induced adiabatic cooling, which may provide a new method to cool a system in experiments.