Fermionic Chern insulator from twisted light with linear polarization

TL;DR

This paper demonstrates that linearly polarized twisted light can induce topological fermionic phases in a graphene-like system by breaking time-reversal symmetry through orbital angular momentum, offering a new method for creating Chern insulators.

Contribution

It introduces a novel mechanism for inducing topological bands using linearly polarized twisted light, expanding the ways to realize Chern insulators beyond circular polarization.

Findings

Topological behavior analogous to static and driven Chern insulators.

Experimental feasibility of realizing the state with twisted light.

Orbital angular momentum in light can break time-reversal symmetry.

Abstract

The breaking of time-reversal symmetry is a crucial ingredient to topological bands. It can occur intrisically in materials with magnetic order, or be induced by external fields, such as magnetic fields in quantum Hall systems, or circularly polarized light fields in Floquet Chern insulators. Apart from polarization, photons can carry another degree of freedom, orbital angular momentum, through which time-reversal symmetry can be broken. In this Letter, we pose the question whether this property allows for inducing topological bands via a linearly polarized but twisted light beam. To this end, we study a graphene-like model of electrons on a honeycomb lattice interacting with a twisted light field. To identify topological behavior of the electrons, we calculate their local markers of Chern number, and monitor the presence of in-gap edge states. Our results are shown to be fully analogous to the behavior found in paradigmatic models for static and driven Chern insulators, and realizing the state is experimentally straightforward. With this, our work establishes a new mechanism for generating Fermionic topological phases of matter that can harness the central phase singularity of an optical vortex beam.