Localization-delocalization transition and $$\mathscr{P}\mathscr{T}$$-symmetry breaking via second-neighbor coupling in a Heisenberg spin chain
Year: 2026
Type: article
Abstract: The exploration of non-Hermitian quantum systems, particularly those governed by parity-time ([Formula: see text])-symmetry, has revealed a rich landscape of unconventional phase transitions and localization phenomena. Spin chains with quasiperiodic potentials and competing Heisenberg interactions provide a versatile framework for probing these effects. In this study, we investigate the dynamical and spectral signatures of [Formula: see text]-symmetry breaking and localization-delocalization transitions in spin chains subjected to a non-Hermitian Aubry-André potential and tunable Heisenberg couplings across nearest ([Formula: see text]) and next-nearest neighbors ([Formula: see text]). Our analysis reveals that increasing [Formula: see text] monotonically shifts the critical point [Formula: see text], while [Formula: see text] induces a non-linear response, generating a distinct minimum in [Formula: see text]. Notably, [Formula: see text] leads to the emergence of partially imaginary eigenvalues beyond [Formula: see text], decoupling the onset of [Formula: see text]-symmetry breaking from the localization transition. Using inverse and normalized participation ratios, we identify three distinct phases: extended, localized, and an intermediate hybrid regime characterized by a mobility edge. To capture the dynamical fingerprints of these phases, we employ time-dependent density distribution, long-time survival probability [Formula: see text], analysis. Extended phases exhibit ballistic spreading and algebraic decay, while localized regimes show spatial confinement and exponential decay. These observables serve as robust indicators of non-Hermitian phase transitions, offering insights beyond static spectral measures. Overall, our findings underscore the critical role of dynamical metrics in characterizing phase structure in non-Hermitian spin systems. As interest in non-equilibrium quantum dynamics continues to grow, such models provide a compelling platform for understanding the interplay between [Formula: see text]-symmetry, localization, and quantum coherence in complex many-body systems.
Source: Scientific Reports
Institution: Shahid Bahonar University of Kerman
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,690
OpenAlex ID: W7161633208
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