thin films

Topologically protected surface states in topological materials provide access to various unconventional transport phenomena. One example in gapless topological semimetals is the unique interplay between bulk and surface Fermi-arc states resulting in an exotic magnetic orbit (Weyl orbit). The Weyl orbit weaves together two spatially-separated Fermi-arc states across the bulk state under the field, allowing the appearance of two-dimensional (2D) quantized conduction even in a 3D system. Here, we report the observation of quantum Hall (QH) states in Dirac semimetal Cd₃As₂ thin films. By controlling Fermi level and band topology of the 3D bulk state with electrostatic gating and chemical-doping-induced topological phase transition, we clarify that the quantized conduction emerges originating from the Weyl orbit. In particular, the successive scan from bulk-dominant conduction to Weyl orbit QH effect, reveals that the emergence of the QH states depends on the bulk Landau level occupation and the induced asymmetry between the film surfaces.