Weyl Nodes of Opposite Chirality in Ferromagnetic WSM

The ferromagnetic Weyl semimetals (WSM), such as Co3Sn2S2, are three-dimensional topological states of matter possessing pairs of Weyl points characterized by the opposite chiralities.We model ferromagnetic WSM by a time reversal symmetry(TRS) broken and inversion symmetry protected Bloch Hamiltonian involving index specifying the chirality of the Weyl points, energy parameter determining the shift of the Weyl nodes, terms capturing the tunnelling effect, exchange field in order to take care of the ferromagnetic(FM) order, and the angle formed by the spin moments and the axis perpendicular to the plane of the system. For the FM order along this axis, the bands of opposite chirality almost linearly cross each other (with band inversion) at Weyl points above and below the Fermi level. The in-plane spin order, however, lacks the presence of the Weyl nodes at some points in the Brillouin zone. We also show that, under certain conditions, the incidence of the circularly polarized optical field (CPOF) leads to the emergence of Weyl semimetals from Dirac semimetals due to broken time-reversal symmetry.