Figure 1: Realization of a topological defect in a microwave resonator chain.
From: Selective enhancement of topologically induced interface states in a dielectric resonator chain
(a) Picture of the experimental microwave realization of the complex Su-Schrieffer-Heeger (SSH) chain. The lattice is composed of 21 identical coupled dielectric cylindrical resonators (5 mm height, 8 mm diameter and a refractive index of 6) sandwiched between two metallic plates (note that the top plate is not shown). To implement dimer chains, the resonators are separated by spacings d1 or d2 with d1<d2, that is, couplings t1>t2. A central dimerization defect is introduced by repeating the spacing d2. The defect creates an interface state at zero energy, a zero mode, whose visibility is enhanced by means of absorptive patches placed on one of the two sublattices. The resulting wavefunction intensity is superimposed onto the chain. (b) Schematic of the complex SSH chain, with A and B sublattices indicated in white and grey, respectively. The strong (weak) coupling strength is represented by a thick (thin) line. In our system, the couplings can be controlled by varying the resonator spacings. The topologically induced zero-mode appears at the interface (red) between α configuration (with strong intradimer coupling) and β configuration (with weak intradimer coupling).
