Quantum transport study of Fermi arc surface states in low-dimensional topological semimetals

Owing to the coupling between open Fermi arcs on opposite surfaces, topological semimetals exhibit a new type of cyclotron orbit in the surface states known as Weyl orbit. It differs from conventional two-dimensional electron states owing to the one-dimensional bulk propagating process along the magnetic field direction through the chiral modes of Weyl fermions. Here we present a systematical quantum transport study of Weyl orbits in Cd₃As₂ and NbAs nanoplates. In Cd₃As₂, the relationship between Fermi level and Fermi surface size of Weyl orbit is investigated. Interestingly, quantum Hall effect is observed under high magnetic field in low-Fermi level samples. The thickness dependence of oscillation phase factor is studied to distinguish the Weyl orbits and possible topological insulator surface states from the finite size effect. In contrast, the Weyl orbits in NbAs exhibit large-frequency oscillations even when the Fermi level is near the Weyl nodes, resulting in exceptional high electrical conductivity far away from a quantized transport. The origin for such distinction between these two materials is discussed.