Surface state hybridization and tunable band inversion in cadmium arsenide thin films

Thin films of the three-dimensional Dirac semimetal cadmium arsenide (Cd₃As₂) provide a route for realizing new topological phases via band structure engineering techniques available in thin film growth. Recently, magnetotransport experiments showed evidence of surface state hybridization in very thin films of (001) Cd₃As₂, opening the possibility of realizing a two-dimensional topological insulator (2D TI) state. In this talk we discuss the evolution of the surface states of (001) Cd₃As₂ films as the thickness is reduced to the regime where hybridization of the surface states occurs. Utilizing magnetotransport measurements performed on gated Hall bar structures, we observe a Landau level spectrum and quantum Hall effect that is in excellent agreement with that predicted for a 2D TI produced via surface state hybridization. Further, we show that a small reduction in film thickness results in a quantum phase transition from a 2D TI state to a trivial insulating state, consistent with theoretical predictions. Our results demonstrate that thin films of Cd₃As₂ are a rich and tunable platform for exploring the novel properties of quantum materials.