Observation of scale-free localized states induced by non-Hermitian defects

TL;DR

This paper reports the experimental discovery of scale-free localized states in non-Hermitian defect systems, where localization length scales with system size, revealing new physics beyond traditional exponential localization.

Contribution

The study introduces and experimentally demonstrates scale-free localized states induced by non-Hermitian defects, expanding the understanding of defect physics in non-Hermitian systems.

Findings

Non-Hermitian defects induce scale-free localization in circuit lattices.

Scale-free localization emerges due to spontaneous parity-time symmetry breaking.

Localization length scales linearly with system size, unlike traditional localized states.

Abstract

Wave localization is a fundamental phenomenon that appears universally in both natural materials and artificial structures and plays a crucial role in understanding the various physical properties of a system. Usually, a localized state has an exponential profile with a localization length independent of the system size. Here, we experimentally demonstrate a new class of localized states called scale-free localized states, which has an unfixed localization length scaling linearly with the system size. Using circuit lattices, we observe that a non-Hermitian defect added to a Hermitian lattice induces an extensive number of states with scale-free localization. Furthermore, we demonstrate that, in a lattice with a parity-time-symmetric non-Hermitian defect, the scale-free localization emerges because of spontaneous parity-time symmetry breaking. Our results uncover a new type of localized states and extend the study of defect physics to the non-Hermitian regime.