Vacancy-like dressed states in topological waveguide QED

TL;DR

This paper introduces a class of topologically protected dressed atom-photon states in waveguide QED, revealing new bound states and photon flux phenomena with potential applications in photonic lattice systems.

Contribution

It provides a novel framework for predicting dressed bound states in topological photonic lattices, linking them to bare photonic bath eigenstates and uncovering new classes of states.

Findings

Identification of vacancy-like dressed states at any coupling strength

Prediction of dressed bound states in topological photonic lattices

Discovery of states with non-zero local photon flux around atoms

Abstract

We identify a class of dressed atom-photon states formingat the same energy of the atom at any coupling strength. As a hallmark, their photonic component is an eigenstate of the bare photonic bath with a vacancy in place of the atom. The picture accommodates waveguide-QED phenomena where atoms behave as perfect mirrors, connecting in particular dressed bound states (BS) in the continuum or BIC with geometrically-confined photonic modes. When applied to photonic lattices, the framework provides a general criterion to predict dressed BS in lattices with topological properties by putting them in one-to-one correspondence with photonic BS. New classes of dressed BS are thus predicted in the photonic Creutz-ladder and Haldane models. In the latter case, states with non-zero local photon flux occur, where an atom is dressed by a photon orbiting around it.