| Summary: | 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·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 hourglass-Type 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.
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