# Subradiant Dimer Excitations of Emitter Chains Coupled to a 1D Waveguide

## TL;DR

This paper demonstrates that chains of emitters coupled to a 1D waveguide can support subradiant dimer states with extended lifetimes, providing analytical insights and a formal equivalence to localized defect states.

## Contribution

It introduces exact analytical expressions for subradiant dimer states in infinite emitter chains and establishes a formal link to localized defect excitations.

## Key findings

- Subradiant dimer states have longer lifetimes than single-excitation subradiant states.
- Analytical expressions for these states are derived for infinite chains.
- The formalism extends to emitters coupled to 3D free space.

## Abstract

This Letter shows that chains of optical or microwave emitters coupled to a 1D waveguide support subradiant states with close pairs of excited emitters, which have longer lifetimes than even the most subradiant states with only a single excitation. Exact, analytical expressions for non-radiative excitation dimer states are obtained in the limit of infinite chains. To understand the mechanism underlying these states, we present a formal equivalence between subradiant dimers and single localized excitations around a chain defect (unoccupied site). Our analytical mapping permits extension to emitter chains coupled to the 3D free space vacuum field.