Weyl semimetal in ultra-thin film of topological insulator multilayer

TL;DR

This paper demonstrates that Weyl semimetals can be realized in ultra-thin topological insulator films by breaking symmetries, leading to novel quantum phases and Weyl nodes at zero energy.

Contribution

It introduces a method to realize Weyl semimetals in ultra-thin topological insulator heterostructures through symmetry breaking.

Findings

Weyl semimetal phase can be achieved in thin films.

Both 3D quantum anomalous Hall and quantum spin Hall phases are realized.

Weyl nodes occur at zero energy under symmetry breaking.

Abstract

In ultra-thin film of topological insulator, the hybridization between the top and bottom surfaces opens an energy gap and forms two degenerate quantum anomalous Hall states, which give rise to a quantum spin Hall state. In this paper, we demonstrate that a Weyl semimetal can be realized in an ultra-thin film of topological insulator heterostructure in a similar way to that of the surface state of a strong three-dimensional (3D) topological insulator studied by Burkov and Balents . We find that the system realizes both 3D quantum anomalous Hall phase and 3D quantum spin Hall phase, and the Weyl nodes occur at zero energy when both time-reversal symmetry and inversion symmetry are explicitly broken by the magnetic field and the structure inversion asymmetry of the thin film.