Multiple triple-point fermions in Heusler compounds

Using the density functional theoretical calculations, we report a new set of topological semimetals X2YZ (X  =  {Cu, Rh, Pd, Ag, Au, Hg}, Y  =  {Li, Na, Sc, Zn, Y, Zr, Hf, La, Pr, Pm, Sm, Tb, Dy, Ho, Tm} and Z  =  {Mg, Al, Zn, Ga, Y, Ag, Cd, In, Sn, Ta, Sm}), which show the existence of multiple topological triple point fermions along four independent  axes. These fermionic quasiparticles have no analogues elementary particle in the standard model. The angle-resolved photoemission spectroscopy is simulated to obtain the exotic topological surface states and the characteristic Fermi arcs. The inclusion of spin–orbit coupling splits the triple-point to two Dirac points. The triple-point fermions are exhibited on the easily cleavable (1 1 1) surface and are well separated from the surface  point, allowing them to be resolved in the surface spectroscopic techniques. This intermediate linearly dispersive degeneracy between Weyl and Dirac points may offer prospective candidates for quantum transport applications.