Title:	From chiral topological dynamics to chiral topological amplification: Real versus imaginary parameters in a Hermitian bosonic chain
Authors:	Estake, Kiran Babasaheb Vishnu, T R Roy, Dibyendu
Keywords:	Photonics Topological phases of matter Non-Hermitian systems Optical parametric oscillators & amplifiers Bogoliubov-de Gennes equations Su-Schrieffer-Heeger model
Issue Date:	16-Dec-2025
Publisher:	Physical Review B
Citation:	Physical Review B, 2025, Vol. 112, AR No. 214314
Abstract:	We propose a Hermitian quadratic bosonic model (QBH) whose dynamical matrix exhibits distinct topological and dynamical phenomena depending on whether the hopping and pairing amplitudes are real or purely imaginary. In the real-parameter regime, the dynamical matrix is unitarily equivalent to four decoupled copies of the sublattice-symmetric non-Hermitian Su-Schrieffer-Heeger (nSSH2) model, thereby inheriting its topological phases and energy spectrum, including the Möbius phase, a gapless topological phase with fractional winding number, having no Hermitian counterpart. We show that the dynamics generated by the QBH Hamiltonian naturally reproduces non-Hermitian time evolution, without invoking nonlinear Schrödinger dynamics or ad hoc normalization. It is demonstrated by analytically calculating the Loschmidt amplitude and computing the dynamical topological order parameter under periodic boundary conditions, which displays a distinct chiral response in the Möbius phase. In contrast, when the hopping and pairing terms are taken to be purely imaginary, the dynamical matrix becomes unitarily equivalent to a different version of the sublattice-symmetric non-Hermitian Su-Schrieffer-Heeger (nSSH1) model that supports only two topological phases, trivial and nontrivial, and the Möbius phase disappears. The latter system exhibits sublattice-dependent chiral amplification under open boundary conditions. We show that this amplification arises from the nontrivial topology of the dynamical matrix, establishing a clear link between topological phase and amplification behavior in the imaginary-parameter regime.
Description:	Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)
URI:	http://hdl.handle.net/2289/8678
ISSN:	2469-9969
Alternative Location:	https://doi.org/10.48550/arXiv.2508.14560 https://doi.org/10.1103/8xgq-ckmh
Copyright:	©2026 American Physical Society.
Appears in Collections:	Research Papers (TP)

Items in RRI Digital Repository are protected by copyright, with all rights reserved, unless otherwise indicated.