Light-driven high-order topological insulators

Light-matter interaction is a powerful tool to manipulate the properties of materials. In particular, the use of a periodic light beam, a technique generically known as Floquet engineering, has the appealing prospect of inducing novel phases of matter that are rare to find in equilibrium. In this work, we propose the use of an intense bicircular light (BCL) field to tune the bulk bands of a topological insulator. Bicircular light consists of a superposition of two circularly polarized light beams with opposite helicities and an integer frequency ratio. The resulting electric field traces a rose pattern in the polarization plane, which allows for a new pathway toward the ultrafast control of magnetic symmetries in the driven system. Using a realistic model for Bi₂Se₃, we theoretically show that a BCL-driven topological insulator undergoes a transition to a high-order topological insulator, which can be tuned by the light-field parameters. We discuss the dependence of the magnetic symmetries of the driven system on the BCL parameters and its consequences on the bulk bands and hinge modes.