Photonic amorphous topological insulator

Peiheng Zhou,Yihao Yang,Baile Zhang,Gui-Geng Liu,Lei Bi,Yidong Chong,Xin Ren,Longjiang Deng,Haoran Xue

doi:10.1038/s41377-020-00368-7

Abstract

The current understanding of topological insulators and their classical wave analogs, such as photonic topological insulators, is mainly based on topological band theory. However, standard band theory does not apply to amorphous phases of matter, which are formed by non-crystalline lattices with no long-range positional order but only short-range order, exhibiting unique phenomena such as the glass-to-liquid transition. Here, we experimentally investigate amorphous variants of a Chern number-based photonic topological insulator. By tuning the disorder strength in the lattice, we demonstrate that photonic topological edge states can persist into the amorphous regime prior to the glass-to-liquid transition. After the transition to a liquid-like lattice configuration, the signatures of topological edge states disappear. This interplay between topology and short-range order in amorphous lattices paves the way for new classes of non-crystalline topological photonic bandgap materials.

Highlights

Photonic topological insulators (PTIs)[1,2,3,4,5] are an emerging class of photonic bandgap materials that can impart “topological protection” to photons, in the same way topological insulator materials do for electrons
The most striking feature enabled by topological protection is the existence of edge states that are protected against perturbations and defects, for which several promising applications have been identified, including robust lasers[6,7,8] and robust optical delay lines[9]
Similar to previous theoretical proposals[42,43], the amorphous PTI that we study consists of gyromagnetic rods that are arranged in computergenerated amorphous lattice patterns and magnetically biased to break time-reversal symmetry

Summary

Introduction

Photonic topological insulators (PTIs)[1,2,3,4,5] are an emerging class of photonic bandgap materials that can impart “topological protection” to photons, in the same way topological insulator materials do for electrons. The most basic class of topological insulators, Chern insulators, have integer band invariants called Chern numbers that are computed using Bloch band states, which in turn owe their existence to the discrete translational symmetry of the lattice[10,11,12,13]. The vast majority of PTIs have been based on periodic lattices[2,13,14,15,16,17,18,19,20,21,22,23,24] such as photonic crystals, which possess both long-range and short-range positional order.

Methods

Results

Conclusion