Chiral Bound States in a staggered array of Coupled Resonators

Abstract

Abstract We study the chiral bound states in a coupled-resonator array with staggered hopping strengths, which interacts with a two-level small atom through a single coupling point or two adjacent ones. In addition to the two typical bound states found above and below the energy bands, this system presents an extraordinary chiral bound state located within the energy gap. We use the chirality to quantify the breaking of the mirror symmetry. We find that the chirality value undergoes continuous changes by tuning the coupling strengths. The preferred direction of the chirality is controlled not only by the competition between the intracell and the intercell hoppings in the coupled-resonator array, but also by the coherence between the two coupling points. In the case with one coupling point, the chirality values varies monotonously with difference between the intracell hopping and the intercell hoppings. While in the case with two coupling points, due to the coherence between the two coupling points the perfect chiral states can be obtained.