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Title: Non-Hermitian topological systems with eigenvalues that are always real
Authors: Long, Yang
Xue, Haoran
Zhang, Baile
Keywords: Science::Physics
Science::Physics::Atomic physics::Solid state physics
Issue Date: 2022
Source: Long, Y., Xue, H. & Zhang, B. (2022). Non-Hermitian topological systems with eigenvalues that are always real. Physical Review B, 105(10), L100102-.
Project: NRF-CRP23-2019-0007
MOE2018‐T2‐1‐022 (S) 
Journal: Physical Review B
Abstract: The effect of non-Hermiticity in band topology has sparked many discussions on non-Hermitian topological physics. It has long been known that non-Hermitian Hamiltonians can exhibit real energy spectra under the condition of parity-time (PT) symmetry - commonly implemented with balanced loss and gain - but only when non-Hermiticity is relatively weak. Sufficiently strong non-Hermiticity, on the other hand, will destroy the reality of energy spectra, a situation known as spontaneous PT-symmetry breaking. Here, based on nonreciprocal coupling, we show a systematic strategy to construct non-Hermitian topological systems exhibiting bulk and boundary energy spectra that are always real, regardless of weak or strong non-Hermiticity. Such nonreciprocal-coupling-based non-Hermiticity can directly drive a topological phase transition and determine the band topology, as demonstrated in a few non-Hermitian systems from one dimensional to two dimensional. Our work develops a theory that can guarantee the reality of energy spectra for non-Hermitian Hamiltonians, and offers an avenue to explore non-Hermitian topological physics.
ISSN: 2469-9950
DOI: 10.1103/PhysRevB.105.L100102
Rights: © 2022 American Physical Society. All rights reserved. This paper was published in Physical Review B and is made available with permission of American Physical Society.
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:SPMS Journal Articles

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