Multifold Topological Point with Quadratic Order in\nBinary Skutterudite Rhodium Triarsenide

The exploration of\ntopological nodal point states has recently\nevolved, moving beyond traditional linear crossings to include higher-order\ndispersions and multifold degeneracies. This study utilizes first-principles\ncalculations to uncover an ideal multifold nodal point of quadratic\norder in the binary skutterudite rhodium triarsenide. The band structures\naround this nodal point show not only simple configuration but also\nclean distribution. Notably, a type-III dispersion condition has also\nbeen identified. When considering the effects of spin–orbit\ncoupling, the nodal point retains both its multiple degeneracy and\nquadratic characteristics, although the band degeneracy transitions\nfrom 3-fold to quadruple. Detailed symmetry argument and model analysis\nhave been provided, and precise band surface distribution has been\nobtained. Furthermore, the material is characterized by multiple significant\narc surface states, as confirmed by the projected topological surface\nstates. The clear separation of these states from the bulk bands facilitates\nexperimental investigation. In summary, the multifold nodal point\nstate identified in this research, along with the corresponding material\ncandidate, presents an exceptional platform for the further study\nof higher-order topological point states, potentially catalyzing advancements\nin this emerging field.