Strain-induced topological transitions in epitaxial films of cadmium arsenide

Abstract

Strain in epitaxial thin films can have a profound influence on their electronic bands. Here, we investigate the influence of epitaxial strains on the electronic states of (001)-oriented cadmium arsenide (Cd3As2) thin films, which are two-dimensional topological insulators. Cd3As2 films were grown coherently on Al1−xInxSb buffer layers with varying degrees of lattice mismatch to Cd3As2, producing in-plane stresses that ranged from compressive to tensile. Using magneto-transport measurements of the Landau levels of the lowest subbands, we show that films under compression remain in the two-dimensional topological insulator state, while a sufficiently large tensile stress induces a transition to a topologically trivial phase. These results qualitatively agree with expectations from theoretical models for these films. At the topological transition, the gap avoids completely closing, and we discuss possible origins.