Strain tuning of the transport gap and magnetic order in Dirac fermion systems

Abstract Using the determinant quantum Monte Carlo method, we explore a rich phase diagram featuring strain-induced metal–insulator and magnetic phase transitions in an interacting two-dimensional Dirac fermion system. Asymmetric strain applied along the zigzag crystal direction drives the semimetallic regime into a band-insulating phase, or it breaks the antiferromagnetic order of the Mott insulator, inducing a nonmagnetic insulating phase under strong correlations. The critical strain required for band gap opening or for a transport phase transition is significantly reduced in the presence of Coulomb repulsion, while increasing interaction strength makes it more difficult for strain to induce a nonmagnetic phase transition. In addition, we measure in detail the band gap modulation by strain and identify a doping effect whereby doping inhibits band gap opening. Our results provide an effective way to tune the transport gap, which could help extend the applications of graphene, whose zero band gap currently limits its use.