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arXiv:2608.08105

Composite-State Localization Beyond the External Landscape in Non-Hermitian Quasicrystals

Tian Zhou, Xue-Bin Wang, Zhongmin Yang, Tao Liu

cond-mat.dis-nncond-mat.mes-hallquant-phSubmitted Aug 8, 2026• Announced Aug 11, 2026
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Abstract

A composite excitation need not inherit the localization behavior of its constituents. We show that an interacting non-Hermitian quasiperiodic ladder realizes a controllable and reversible localization inversion between composite and unbound excitations, where internal configuration, rather than only the external potential, becomes a control parameter for localization. Opposite complex potentials on the two legs cancel at first order for a same-rung pair but act directly on separated particles, allowing extended composite states to persist while the unpaired sector becomes localized. A strong-coupling theory identifies the composite state as an emergent weakly modulated non-Hermitian quasicrystal generated by virtual unpaired configurations. Breaking the potential antisymmetry restores a direct modulation of the composite band and reverses the localization hierarchy. Engineering configuration-space pathways further stabilizes an extended composite band embedded within a localized continuum, the inverse of the conventional bound-state-in-the-continuum scenario. Our results establish internal configuration as a reversible control parameter for localization.

Comments
13 pages, 10 figures

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