Weyl Semimetal — Fermi Arc Surface States
Bulk Weyl nodes connected by topological surface arcs
In a Weyl semimetal, bands cross at pairs of Weyl nodes with opposite chirality (topological charge ±1). By the bulk-boundary correspondence, the surface Brillouin zone contains open Fermi arcs connecting the projections of bulk Weyl nodes. These arcs are topologically protected and have been observed in TaAs, NbAs, and WTe₂. The chiral nature leads to the chiral anomaly: non-conservation of chiral charge in parallel E and B fields.