Magnetic-field induced semimetal in topological crystalline insulator thin films

• The band structure of topological crystalline insulator thin films can be controlled by applying in-plane magnetic field.
• At the gap closing magnetic field, a pair of gapless cones carrying opposite chirarities emerge.
• A pair of gapless points have opposite vortex numbers.
• This is a reminiscence of a pair of Weyl cones in 3D Weyl semimetal.
• A magnetic-field induced semimetal–semiconductor transition occurs in 2D material.

We investigate electromagnetic properties of a topological crystalline insulator (TCI) thin film under external electromagnetic fields. The TCI thin film is a topological insulator indexed by the mirror-Chern number. It is demonstrated that the gap closes together with the emergence of a pair of gapless cones carrying opposite chirarities by applying in-plane magnetic field. A pair of gapless points have opposite vortex numbers. This is a reminiscence of a pair of Weyl cones in 3D Weyl semimetal. We thus present an a magnetic-field induced semimetal–semiconductor transition in 2D material. This is a giant-magnetoresistance, where resistivity is controlled by magnetic field. Perpendicular electric field is found to shift the gapless points and also renormalize the Fermi velocity in the direction of the in-plane magnetic field.