Engineering Dirac states in graphene: Coexisting type-I and type-II Floquet-Dirac fermions

TL;DR

This paper demonstrates how to engineer coexisting type-I and type-II Floquet-Dirac fermions in graphene using light, revealing new topological states and potential for advanced optoelectronic applications.

Contribution

It introduces a method to create and control coexisting Floquet-Dirac fermions in graphene through light tuning, revealing novel topological edge states.

Findings

Coexistence of type-I and type-II Floquet-Dirac fermions in graphene.

Emergence of topologically nontrivial edge states connecting the two types.

Experimental signatures suggest the states are accessible via photoelectron spectroscopy.

Abstract

The coupling of monochromatic light fields and solids introduces nonequilibrium Floquet states, offering opportunities to create and explore new topological phenomena. Using combined first-principles and Floquet analysis we show that one can freely engineer Floquet-Dirac fermions (FDFs) in graphene by tuning the frequency and intensity of linearly polarized light. Not only type-II FDFs are created, but they also coexist with type-I FDFs near the Fermi level. Intriguingly, novel topologically nontrivial edge states connecting type-I and type-II Floquet-Dirac points emerge in photodriven graphene, providing an ideal channel to realize electron transport between the two types of Dirac states. Simulating time- and angle-resolved photoelectron spectroscopy suggests that the new coexisting state of type-I and type-II fermions is experimentally accessible. This work implies that a rich FDF phenomenon can be engineered in atomically thin graphene, hinting for developments of novel optoelectronic and quantum computing devices.