Quaternary Heusler alloy: An ideal platform to realize triple point fermions

We predict the occurrence of triply degenerate nodal points (TP) in the band structure of a series of quaternary Heusler alloys using first principle electronic structure calculation and appropriate point group symmetry analysis. TPs are usually formed due to the interplay of threefold rotational, mirror, and time reversal symmetries in the momentum space. We projected these TPs onto the (111) and (100) surfaces that lead to the formation of topological Fermi arcs, which may further be detected by scanning tunneling spectroscopy and angle resolved photoemission spectroscopy. These Fermi arcs arise due to the symmetry protected band degeneracies, which are robust and cannot be avoided due to the nontrivial band topology. A great advantage of the currently studied systems over other existing compounds is that the TPs in this class of systems are located far away from the Γ point along C₃ axes. This helps to overcome the experimental difficulties over previously studied hexagonal and HgTe-type compounds.