Exceptional Surfaces in PT-Symmetric Photonic Systems

TL;DR

This paper introduces the concept of two-dimensional exceptional surfaces in PT-symmetric photonic systems, expanding the understanding of non-Hermitian topological phenomena and their physical implications.

Contribution

It presents the design and analysis of 2D exceptional surfaces protected by symmetries, using symmetry-preserving deformations of topological nodal lines, and demonstrates their realization in 3D photonic crystals.

Findings

Identification of symmetry-protected exceptional surfaces

Simulation of PT-symmetric 3D photonic crystal with exceptional surfaces

Analysis of topological and physical properties of these surfaces

Abstract

Exceptional points in non-Hermitian systems have recently been shown to possess nontrivial topological properties, and to give rise to many exotic physical phenomena. However, most studies thus far have focused on isolated exceptional points or one-dimensional lines of exceptional points. Here, we substantially expand the space of exceptional systems by designing two-dimensional surfaces of exceptional points, and find that symmetries are a key element to protect such exceptional surfaces. We construct them using symmetry-preserving non-Hermitian deformations of topological nodal lines, and analyze the associated symmetry, topology, and physical consequences. As a potential realization, we simulate a parity-time-symmetric 3D photonic crystal and indeed find the emergence of exceptional surfaces. Our work paves the way for future explorations of systems of exceptional points in higher dimensions.