Weyl Semimetallic State in the Rashba–Hubbard Model

We investigate the Hubbard model with the Rashba spin–orbit coupling on a square lattice. The Rashba spin–orbit coupling generates two-dimensional Weyl points in the band dispersion. In a system with edges along [11] direction, zero-energy edge states appear, while no edge state exists for a system with edges along an axis direction. The zero-energy edge states with a certain momentum along the edges are predominantly in the up-spin state on the right edge, while they are predominantly in the down-spin state on the left edge. Thus, the zero-energy edge states are helical. By using a variational Monte Carlo method for finite Coulomb interaction cases, we find that the Weyl points can move toward the Fermi level by the correlation effects. We also investigate the magnetism of the model by the Hartree–Fock approximation and discuss weak magnetic order in the weak-coupling region.