Seeing topological winding number and band inversion in photonic dimer chain of split-ring resonators
Jun Jiang, Jie Ren, Zhiwei Guo, Weiwei Zhu, Yang Long, Haitao Jiang, Hong Chen
Abstract
The exotic topological states have advanced the exploration for topological characteristics, such as invariant topological orders and band inversion. Here, we experimentally construct photonic dimer chains composed of split-ring resonators to exhibit interesting topological properties with different orientation angles. By using the method of near-field detection, we measure the dispersion relation and sublattice pseudospin vectors of different orientated configurations, which immediately determines the associated winding number of bulk bands as the topological invariant. Moreover, the sublattice pseudospin vector inversion observed at band edges indicates the band inversion and the associated topological phase transition, which is reconfirmed by measuring the band-edge mode parity and symmetry of the split-ring resonator cell. Our results not only directly show the topological winding number, band inversion, pseudospin, and the symmetries of band-edge states in experiments, but also reveal the great potential of the split-ring resonator platform to experimentally explore the advanced topological characteristics, such as higher winding numbers or higher Chern numbers in more complex setups.