Fundamental constraints on the observability of non-Hermitian effects in passive systems

Abstract

Utilizing scattering theory, we quantify the consequences of physical constraints that limit the visibility of non-Hermitian effects in passive devices. The constraints arise from the fundamental requirement that the system obeys causality, and can be captured concisely in terms of an internal time-delay operator, which furthermore provides a direct quantitative measure of the visibility of specific non-Hermitian phenomena in the density of states. We illustrate the implications by contrasting different symmetry classes and non-Hermitian effects, including exceptional points and the non-Hermitian skin effect, whose underlying extreme mode nonorthogonality turns out to be effectively disguised.

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Cited by in corpus (8)

• Topological Non-Hermitian skin effect
• Transient non-Hermitian skin effect
• High-order spectral singularity
• Uniform response theory of non-Hermitian systems: Non-Hermitian physics beyond the exceptional point
• Quantum metric dependent anomalous velocity in systems subject to complex electric fields
• Optical non-Hermitian skin effect in two-dimensional uniform media
• Exceptional points in perturbed dielectric spheres: A resonant-state expansion study
• Observation of non-Hermitian point gap in photonic crystals