High throughput screening for Weyl semimetals with S4 symmetry

IMAGE: The definition of χ in systems with S4 symmetry on the orange S surface. The system in (b) has C2,110 symmetry. see more

Credit: @ Science China Press

Using systems symmetries, people can define various topological invariants to describe different topological states. Topological materials can be discovered precisely by calculating the topological invariants. Recently, researchers have found that irreducible representations and compatibility relationships can be used to determine whether a material is a nontrivial / trivial topological insulator (satisfying compatibility relations) or topological semimetal (violating compatibility relations), the which leads to a large number of topological materials predicted by theoretical calculations. However, Weyl semimetals go beyond this paradigm because the existence of Weyl fermions does not require any symmetry protection (with the exception of lattice translation symmetries). At present, people usually take a very dense grid in the three dimensional Brillouin zone to look for Weyl fermions with zero band gap. Due to the large amount of calculations required, this method is very …

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