Tunable Chiral Bound States in a Dimer Chain of Coupled Resonators

TL;DR

This paper investigates tunable chiral bound states in a 1D dimer chain coupled with a two-level emitter, revealing how coupling configurations and parameters influence the emergence and properties of these states.

Contribution

It demonstrates the controllable formation of chiral bound states through different coupling schemes and parameter adjustments in a resonator chain system.

Findings

Nonlocal coupling induces three chiral bound states.

Chirality can be tuned by energy differences and coupling strengths.

Perfect chiral bound states are achievable via destructive interference.

Abstract

We study the chiral feature in a system composed of one two-level emitter (TLE) and a one dimensional (1D) dimer chain of coupled resonators with the alternate single-photon energies. In the single-excitation subspace, this system not only possesses two energy bands with propagating states, but also possesses chiral bound states. The number of chiral bound states depends on the coupling forms between the TLE and the dimer chain. It is found that when the TLE is locally coupled to one resonator of the dimer chain, the bound-state that has mirror reflection symmetry is not a chiral one. When the TLE is nonlocally coupled to two adjacent resonators, three chiral bound states arise due to the mirror symmetry breaking. The chirality of these bound states can be tuned by changing the energy differences of single photon in the adjacent resonators, the coupling strengths and the transition energy of the TLE. The chirality behaviour of the ordinary two bound states outside the energy bands is quite different from the one of the emerging bound state inside the energy gap. The almost perfect chiral bound states can be achieved at certain parameters as a result of completely destructive interference.