Optical conductivity of the threefold Hopf semimetal

A multifold Hopf semimetal is a topological point node possessing an anisotropy in the internal electronic structure, e.g., dipole structure of Berry curvature. In this paper, unique features threefold semimetals terms optical conductivity are theoretically investigated with minimal theoretical model by using linear response theory for linearly polarized photon. The frequency spectrum shows anisotropic dependence on polarization angle incident photon even if band completely isotropic. longitudinal depends and possesses steplike changes spectrum. has varying number steps orientation axis. We reveal that attributed to symmetries preserving fermion qualitatively different from so-called spin-1 fermion. also induces Hall current, but it vanishes axis parallel numerical calculations show these characteristic can be observed nonzero temperature disorder.