# 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.

## Key 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.

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Source: https://tomesphere.com/paper/1901.10058