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Main Authors:	Rahul, S, Palumbo, Giandomenico
Format:	Preprint
Published:	2025
Subjects:	Mesoscale and Nanoscale Physics Optics Quantum Physics
Online Access:	https://arxiv.org/abs/2509.15102
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author	Rahul, S Palumbo, Giandomenico
author_facet	Rahul, S Palumbo, Giandomenico
contents	Zero indirect gaps in band models are typically viewed as unstable and achievable only through fine-tuning. Recent works, however, have revealed robust semimetallic phases in Hermitian systems where the indirect gap remains pinned at zero over a finite parameter range. Here, we extend this paradigm to non-Hermitian lattice models by studying a one-dimensional diamond-like system with gain and loss. We show that the zero indirect band gap in the real part of the spectrum remains stable in the presence of non-Hermitian perturbations and identify the parameter regime in which this robustness persists. We find that the appearance of the zero indirect gap coincides with the suppression of the non-Hermitian skin effect. Our results reveal new connections between indirect gaps, exceptional points and non-Hermitian skin effect, opening avenues for experimental realizations.
format	Preprint
id	arxiv_https___arxiv_org_abs_2509_15102
institution	arXiv
publishDate	2025
record_format	arxiv
spellingShingle	Zero Indirect Band Gap in Non-Hermitian Systems Rahul, S Palumbo, Giandomenico Mesoscale and Nanoscale Physics Optics Quantum Physics Zero indirect gaps in band models are typically viewed as unstable and achievable only through fine-tuning. Recent works, however, have revealed robust semimetallic phases in Hermitian systems where the indirect gap remains pinned at zero over a finite parameter range. Here, we extend this paradigm to non-Hermitian lattice models by studying a one-dimensional diamond-like system with gain and loss. We show that the zero indirect band gap in the real part of the spectrum remains stable in the presence of non-Hermitian perturbations and identify the parameter regime in which this robustness persists. We find that the appearance of the zero indirect gap coincides with the suppression of the non-Hermitian skin effect. Our results reveal new connections between indirect gaps, exceptional points and non-Hermitian skin effect, opening avenues for experimental realizations.
title	Zero Indirect Band Gap in Non-Hermitian Systems
topic	Mesoscale and Nanoscale Physics Optics Quantum Physics
url	https://arxiv.org/abs/2509.15102

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