Topological surface states in strained Cd3As₂ thin films

Cd₃As₂ is a Dirac semi-metal with two Dirac nodes near the Γ point in the first Brillouin zone aligned along the crystallographic c-axis. The structure of Cd₃As₂ is rather complicated with a large unit cell and it is typically grown along the (112) direction, which does result in a projection of the Fermi arc states on the (112) surface. The Dirac points are protected by inversion and C₄ symmetry about the tetragonal c-axis. In recent experiments, the inversion symmetry can be broken in thin films, and the C₄ symmetry can be broken by a bi-axial strain perpendicular to the c-axis [1]. This brings up the question of what happens to the Fermi arc states in the ultra-thin film limit and in the presence of broken symmetries. We are using a simple description of the low energy physics to examine the behavior of the Fermi arc states. As an example, when inversion symmetry is broken, so is the symmetry of the Fermi arc states near the Dirac points, and the two-fold degeneracy of the Dirac cones is lifted.

[1] M. Goyal, H. Kim, T. Schumann, L. Galletti, A. A. Burkov, and S. Stemmer, Phys. Rev. Mat. 3, 064204 (2019).