Seeing Topological Order and Band Inversion in Optical Diatomic Chain

TL;DR

This paper demonstrates the realization and measurement of topological order and band inversion in a 1D optical diatomic chain using split ring resonators, revealing topological phase transitions through experimental dispersion and pseudo-spin analysis.

Contribution

It introduces a novel optical diatomic chain platform with electric-magnetic couplings to experimentally observe topological features like winding numbers and band inversion.

Findings

Measured dispersion relationships and sub-lattice pseudo-spin vectors.

Observed sub-lattice pseudo-spin vector inversion at band-edges.

Confirmed topological phase transition via symmetry exchanges.

Abstract

Recent realizations of exotic topological states in condensed matter and cold atoms have advanced the exploration for topological characteristics, such as invariant topological orders and band inversion. Here we construct a 1D optical diatomic system made of split ring resonators with electric-magnetic couplings to implement the topological features. We experimentally measure the dispersion relationship and sub-lattice pseudo-spin vectors by detecting field strength distributions, which determines the accompanying winding number of bulk band as the topological order. The sub-lattice pseudo-spin vector inversion observed at band-edges evidences the band inversion. We further reconfirm the band-inversion-induced topological phase transition by measuring the symmetry exchanges at band-edges. These results have shown the great potential of split ring resonator platform to experimentally explore the advanced topological characteristics, such as high winding numbers or even high Chern numbers in more exotic setups.