Simple formulas of directional amplification from non-Bloch band theory

• URL: http://arxiv.org/abs/2004.09529v2
• Date: Tue, 29 Jun 2021 05:19:01 GMT
• Title: Simple formulas of directional amplification from non-Bloch band theory
• Authors: Wen-Tan Xue, Ming-Rui Li, Yu-Min Hu, Fei Song, Zhong Wang
• Abstract summary: Green's functions are fundamental quantities that determine the linear responses of physical systems. The recent developments of non-Hermitian systems, therefore, call for Green's function formulas of non-Hermitian bands. Here, based on the non-Bloch band theory, we obtain simple Green's function formulas of general one-dimensional non-Hermitian bands.
• Score: 1.467695648564673
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Green's functions are fundamental quantities that determine the linear responses of physical systems. The recent developments of non-Hermitian systems, therefore, call for Green's function formulas of non-Hermitian bands. This task is complicated by the high sensitivity of energy spectrums to boundary conditions, which invalidates the straightforward generalization of Hermitian formulas. Here, based on the non-Bloch band theory, we obtain simple Green's function formulas of general one-dimensional non-Hermitian bands. Furthermore, in the large-size limit, these formulas dramatically reduce to finding the roots of a simple algebraic equation. As an application, our formulation provides the desirable formulas for the defining quantities, the gain and directionality, of directional amplification. Thus, our formulas provide an efficient guide for designing directional amplifiers.

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