# Topological Floquet Engineering of Twisted Bilayer Graphene

## TL;DR

This paper explores how circularly polarized laser pulses can induce topological phases in twisted bilayer graphene above the magic angle, revealing tunable Floquet topological properties and expanding the potential for twistronics and non-equilibrium physics.

## Contribution

It demonstrates Floquet engineering of topological phases in twisted bilayer graphene using a full Moiré-unit-cell tight-binding model, highlighting tunability via bias voltage and twisting.

## Key findings

- Circularly polarized light induces topologically nontrivial Floquet bands.
- Bias voltage enables exploration of the full topological phase diagram.
- Twisting allows tuning of electronic energy scales to match realistic driving frequencies.

## Abstract

We investigate the topological properties of Floquet-engineered twisted bilayer graphene above the magic angle driven by circularly polarized laser pulses. Employing a full Moir\'e-unit-cell tight-binding Hamiltonian based on first-principles electronic structure we show that the band topology in the bilayer, at twisting angles above 1.05$^\circ$, essentially corresponds to the one of single-layer graphene. However, the ability to open topologically trivial gaps in this system by a bias voltage between the layers enables the full topological phase diagram to be explored, which is not possible in single-layer graphene. Circularly polarized light induces a transition to a topologically nontrivial Floquet band structure with the Berry curvature of a Chern insulator. Importantly, the twisting allows for tuning electronic energy scales, which implies that the electronic bandwidth can be tailored to match realistic driving frequencies in the ultraviolet or mid-infrared photon-energy regimes. This implies that Moir\'e superlattices are an ideal playground for combining twistronics, Floquet engineering, and strongly interacting regimes out of thermal equilibrium.