Parity-Induced Thermalization Gap in Disordered Ring Lattices

TL;DR

This paper experimentally demonstrates a parity-dependent thermalization gap in disordered ring photonic lattices, revealing how topology and symmetry influence photon statistics amidst disorder and localization effects.

Contribution

First experimental observation of a parity-induced thermalization gap in strongly disordered ring photonic structures, highlighting the role of lattice topology and chiral symmetry.

Findings

Parity determines photon statistics in disordered ring lattices.

Thermalization gap persists at small scales despite localization.

Strong disorder leads to Anderson localization overshadowing the gap.

Abstract

The gaps separating two different states widely exist in various physical systems: from the electrons in periodic lattices to the analogs in photonic, phononic, plasmonic systems, and even quasicrystals. Recently, a thermalization gap, an inaccessible range of photon statistics, was proposed for light in disordered structures [Nat. Phys. 11, 930 (2015)], which is intrinsically induced by the disorder-immune chiral symmetry and can be reflected by the photon statistics. The lattice topology was further identified as a decisive role in determining the photon statistics when the chiral symmetry is satisfied. Being very distinct from one-dimensional lattices, the photon statistics in ring lattices are dictated by its parity, i.e, odd or even sited. Here, we for the first time experimentally observe a parity-induced thermalization gap in strongly disordered ring photonic structures. In a limited scale, though the light tends to be localized, we are still able to find clear evidence of the parity-dependent disorder-immune chiral symmetry and the resulting thermalization gap by measuring photon statistics, while strong disorder-induced Anderson localization overwhelms such a phenomenon in larger-scale structures. Our results shed new light on the relation among symmetry, disorder, and localization, and may inspire new resources and artificial devices for information processing and quantum control on a photonic chip.