Type-II Dirac point in RbAg5Se3

Using first-principles calculations and low-energy effective model analysis, we propose that silver selenide-based RbAg5Se3 compound is an ideal type-II Dirac semimetal. There is a pair of Dirac points appearing at about 25.68 meV below the Fermi energy. The Dirac points existing on the kz axis are protected by C4z rotation symmetry in addition to PT symmetry. Meanwhile, the system is also characterized by a nontrivial Z2 topological invariant. The long clean Fermi arcs exist on the (010) surface, connecting the projections of the Dirac points. In addition, the Landau levels of the type-II Dirac points under magnetic field are also calculated. Our discovery not only adds one promising candidate into the type-II Dirac semimetals family but also provides an ideal platform for the study of topological phase transitions.