Merging of Dirac points and Floquet topological transitions in AC driven graphene

TL;DR

This paper demonstrates how an in-plane AC electric field can manipulate Dirac points in graphene, enabling topological transitions and merging of Dirac points through frequency and polarization tuning, using Floquet theory.

Contribution

It introduces a method to control and merge Dirac points in graphene via AC fields, revealing new topological transitions not previously observed in electronic systems.

Findings

Dirac points can be moved by field amplitude and polarization.

Multi-photon processes create additional Dirac point pairs.

Frequency tuning enables merging transitions.

Abstract

We investigate the effect of an in-plane AC electric field coupled to electrons in the honeycomb lattice and show that it can be used to manipulate the Dirac points of the electronic structure. We find that the position of the Dirac points can be controlled by the amplitude and the polarization of the field for high frequency drivings, providing a new platform to achieve their merging, a topological transition which has not been observed yet in electronic systems. Importantly, for lower frequencies we find that the multi-photon absorptions and emissions processes yield the creation of additional pairs of Dirac points. This provides an additional method to achieve the merging transition by just tuning the frequency of the driving. Our approach, based on Floquet formalism, is neither restricted to specific choice of amplitude or polarization of the field, nor to a low energy approximation for the Hamiltonian.