Cycling Fermi arc electrons with Weyl orbits

The Weyl orbit refers to a new type of cyclotron orbit recently proposed in Weyl semimetals. This is a surface–bulk hybrid orbit that can be modulated by thickness and external fields. Recently, the Weyl orbit has been used to realize the 3D quantum Hall effect, and subsequent rapid progress in experiments promise a new understanding of higher-dimension quantum Hall physics. In this Perspective, we review the theoretical background and the current experimental status of the Weyl orbit, present the extension of Weyl orbit physics in realizing the 3D quantum Hall effect and further discuss the opportunities in tuning topological quantum states and realizing device applications provided by the concept of the Weyl orbit. The Weyl orbit is a type of cyclotron orbit that appears in topological semimetals. This Perspective discusses the Weyl orbit in the context of the 3D quantum Hall effect and provides an outlook on new phenomena that can arise from these states.