Strong-field physics in three-dimensional topological insulators

In this work, the authors theoretically investigate high-order harmonic generation from a three-dimensional topological insulator. They find that the surface states enhance the harmonic yield for circularly polarized fields. Such behaviors could be linked to the conical shape of the energy bands near the Dirac point in the Brillouin zone, as well as the associated interband transition dipole moments that form vortexlike features at the cusp of the cone.