Ideal hourglass-type charge-three Weyl fermions in spinless systems

Hourglass -type Weyl fermions with the maximally topological charge of |C| = 3, namely hourglass -type charge -three Weyl fermions (CTWFs), have seldom been reported due to the nonnegligible spin -orbit coupling effect and Pauli exclusion principles. Here, based on symmetry arguments and the low -energy effective k center dot p model, we confirm that two chiral space groups (SGs), i.e., SG P63 (No. 173) and SG P6322 (No. 182), can host ideal hourglass -type CTWFs in spinless systems. Moreover, we take Li2CO4 as a concrete example to show the ideal hourglass -type CTWFs, which possess ultralong sextuple- and triple-helicoid Fermi arcs, making them easier to be detected by experiments. Our work not only offers an avenue to search for ideal hourglasstype CTWFs but also provides a promising platform for experiments to verify this kind of unconventional quasiparticles with the ultralong sextuple- and triple-helicoid surface arcs.