Topological Surface States of Cadmium Arsenide Thin Films

Thin films of the topological semimetal cadmium arsenide (Cd₃As₂) can host different types of topological surface states, depending on their crystallographic orientation¹. Here we elucidate the nature of these surface states by comparing films grown in (112) and (001) orientations, respectively. For (112) thin films Weyl orbits², involving Fermi arcs on opposite surfaces, have been predicted, which should exhibit a thickness-dependent phase in quantum oscillations. We compare quantum transport in films of varying thickness at apparently identical gate-tuned carrier concentrations and find no clear dependence of the relative phase of the quantum oscillations on the sample thickness³. Small variations in carrier densities, difficult to detect in low-field Hall measurements, lead to shifts in quantum oscillations that are commensurate with previously reported phase shifts. By contrast, measurements of the quantum Hall effect in (001)-oriented thin films show evidence of topological insulator-like states at bottom and top interfaces. Quantum oscillation measurements in different geometries are used to determine interactions between the surfaces.
1. Wang et al. Phys. Rev. B 88, 125427 (2013)
2. Potter et al. Nat. Commun. 10, 1038 (2014)
3. Galletti et al. Phys. Rev. B 99, 201401 (2019)