Filling-Sensitive Spectral Complexity from Hilbert-Space Holonomy in Fragmented Non-Hermitian Systems

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Auteurs principaux: Wang, Jiong-Hao, Zelenayova, Maria, Ekman, Christopher, Bergholtz, Emil J.
Format: Preprint
Publié: 2026
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author Wang, Jiong-Hao
Zelenayova, Maria
Ekman, Christopher
Bergholtz, Emil J.
author_facet Wang, Jiong-Hao
Zelenayova, Maria
Ekman, Christopher
Bergholtz, Emil J.
contents We show that Hilbert-space holonomy provides a geometric organizing principle for spectral reality in fragmented non-Hermitian many-body systems, complementary to conventional symmetry protection. In two minimal fragmented models, complex spectra can arise only within the most symmetric sectors: half filling in the fermion model and zero magnetization in the spin chain. Adding or removing a single particle, or flipping a single spin, renders the spectra entirely real despite unchanged periodic boundary conditions, reminiscent of boundary-condition sensitivity in systems with a non-Hermitian skin effect. We explain this by viewing nonreciprocal hopping amplitudes as a discrete gauge field on the Krylov graph: trivial holonomy permits a diagonal similarity transformation to the Hermitian limit, whereas nontrivial holonomy obstructs it and allows complex spectra. In certain regimes, trivial holonomy admits an emergent-boundary interpretation, and longer-range models exhibit finite real and complex regions governed by the same criterion.
format Preprint
id arxiv_https___arxiv_org_abs_2605_19740
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Filling-Sensitive Spectral Complexity from Hilbert-Space Holonomy in Fragmented Non-Hermitian Systems
Wang, Jiong-Hao
Zelenayova, Maria
Ekman, Christopher
Bergholtz, Emil J.
Strongly Correlated Electrons
Mesoscale and Nanoscale Physics
Statistical Mechanics
Optics
Quantum Physics
We show that Hilbert-space holonomy provides a geometric organizing principle for spectral reality in fragmented non-Hermitian many-body systems, complementary to conventional symmetry protection. In two minimal fragmented models, complex spectra can arise only within the most symmetric sectors: half filling in the fermion model and zero magnetization in the spin chain. Adding or removing a single particle, or flipping a single spin, renders the spectra entirely real despite unchanged periodic boundary conditions, reminiscent of boundary-condition sensitivity in systems with a non-Hermitian skin effect. We explain this by viewing nonreciprocal hopping amplitudes as a discrete gauge field on the Krylov graph: trivial holonomy permits a diagonal similarity transformation to the Hermitian limit, whereas nontrivial holonomy obstructs it and allows complex spectra. In certain regimes, trivial holonomy admits an emergent-boundary interpretation, and longer-range models exhibit finite real and complex regions governed by the same criterion.
title Filling-Sensitive Spectral Complexity from Hilbert-Space Holonomy in Fragmented Non-Hermitian Systems
topic Strongly Correlated Electrons
Mesoscale and Nanoscale Physics
Statistical Mechanics
Optics
Quantum Physics
url https://arxiv.org/abs/2605.19740