Type-II nodal line in RuSb and TaB2 compounds*

In this work, we investigate the topological property and electronic structure of RuSb compound using the first-principles method. The band structure of RuSb without spin-orbit coupling (SOC) exhibits four nodal lines located at the mirror plane kz=0 and the energy of nodal points changes along the nodal line. The tilting of the nodal line located at kz=0 changes which leads to the realization of a mixture of type-I and type-II or hybrid nodal lines. These nodal lines are highly anisotropic and are protected by the mirror symmetry when SOC is ignored. The inclusion of SOC leads to the formation of small gaps along the nodal lines. The corresponding Fermi surface sheets with and without SOC were obtained. The surface states calculation shows the existence of nontrivial surface states characteristic of this material. We also identified the TaB₂ as the type-II and hybrid nodal line structure.