Generalised Brillouin Zone for Non-Reciprocal Systems


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Date

2024-08

Publication Type

Report

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Abstract

Recently, it has been observed that the Floquet-Bloch transform with real quasiperiodicities fails to capture the spectral properties of non reciprocal systems. The aim of this paper is to introduce the notion of a generalised Brillouin zone by allowing the quasiperiodicities to be complex in order to rectify this. It is proved that this shift of the Brillouin zone into the complex plane accounts for the unidirectional spatial decay of the eigenmodes and leads to correct spectral convergence properties. The results in this paper clarify and prove rigorously how the spectral properties of a finite structure are associated with those of the corresponding semi-infinitely or infinitely periodic lattices and give explicit characterisations of how to extend the Hermitian theory to non-reciprocal settings. Based on our theory, we characterise the generalised Brillouin zone for both open boundary conditions and periodic boundary conditions. Our results are consistent with the physical literature and give explicit generalisations to the k-Toeplitz matrix cases.

Publication status

published

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Volume

2024-22

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Publisher

Seminar for Applied Mathematics, ETH Zurich

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Subject

Generalised Brillouin zone; Non-reciprocal systems; Non-Hermitian skin effect; Toeplitz matrices and operators; Laurent operators; Spectral convergence

Organisational unit

09504 - Ammari, Habib / Ammari, Habib check_circle

Notes

Funding

200307 - Mathematics of dielectric artificial media (SNF)

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