Mott transition in the $\ddot{I}€$-flux SU($4$) Hubbard model on a square lattice

Abstract

We employ the projector quantum Monte Carlo simulations to study the ground-state properties of the square-lattice SU(4) Hubbard model with a $\ddot{I}€$ flux per plaquette. In the weak coupling regime, its ground state is in the gapless Dirac semi-metal phase. With increasing repulsive interaction, we show that, a Mott transition occurs from the semimetal to the valence bond solid, accompanied by the $Z_4$ discrete symmetry breaking. Our simulations demonstrate the existence of a second-order phase transition, which confirms the Ginzburg-Landau analysis. The phase transition point and the critical exponent $\hat{I}\cdot$ are also estimated. To account for the effect of a $\ddot{I}€$ flux on the ordering in the strong coupling regime, we analytically derive by the perturbation theory the ring-exchange term which describes the leading-order difference between the $\ddot{I}€$-flux and zero-flux SU(4) Hubbard models.

8 pages, 9 figures