ν = 0 quantum Hall state in a cadmium arsenide thin film

Abstract

Graphene and topological insulators can feature a unique quantum Hall state with a filling factor of ν = 0 that supplies a wealth of information about the nature of the underlying electronic states. Here, we report on the observation of a ν = 0 Hall state in magnetotransport experiments on a 20-nm-thin, (001)-oriented cadmium arsenide film that is tuned by a gate voltage. While cadmium arsenide is a topological semimetal as a bulk material, thin films can host topological insulator phases. At high magnetic fields, we observe a highly resistive ν = 0 Hall state that we attribute to a widening gap between two zeroth Landau levels as the magnetic field is increased. We discuss possible scenarios that could give rise to the lifting of the degeneracy of zeroth Landau levels. Our results are most consistent with a scenario of hybridization of the topological surface states induced by quantum confinement.

Two-Dimensional Topological Insulator State in Cadmium Arsenide Thin Films

“…As the Cd3As2 film thickness is further reduced, theory predicts a transition to a 2D TI (quantum spin Hall insulator) with a wide energy gap [14]. Recently, we reported evidence of surface state hybridization in a 20 nm-thin Cd3As2 thin film [23], an essential step towards a 2D TI. Here, we present the first experimental evidence of a 2D TI state in (001)-oriented Cd3As2 films.…”