Magnonic frequency-comb enhancement via a pseudo-exceptional point in a driven magnon-polariton system
Phys. Rev. Applied 26, 044046 – Published 16 October, 2026
DOI: https://doi.org/10.1103/h2wj-1r5b
Abstract
Non-Hermitian systems exhibit unique properties, with exceptional points (EPs) serving as a prominent example of singular spectral degeneracy that has attracted broad interest. This interest now encompasses magnon-polariton platforms. Here, we disclose a fundamentally distinct picture in a strongly driven magnon-polariton Floquet system: a pseudo-exceptional point (PEP). Analytical derivation and macrospin simulation reveal that both the mode’s frequency and its decay rate remain finite on both sides of the PEP—a definitive departure from the characteristic eigenvalue splitting of a conventional EP. Crucially, we demonstrate that the key spectral features, particularly in the weak-driving limit, are governed by the damping coefficient, confirming the non-Hermitian origin of the phenomenon. This picture originates from the Floquet dynamics of a single driven mode and provides a natural mechanism for key nonlinear phenomena, such as frequency combs. Our work clarifies the underlying physics of non-Hermitian critical behavior in driven-dissipative spin systems and establishes the PEP as a framework, offering a robust and designable route to generating nonlinear phenomena in Floquet-engineered systems.
