Exceptional points as signatures of dynamical magnetic phase transitions

TL;DR

This paper explores how exceptional points in non-Hermitian magnetic systems influence spin dynamics, revealing a rich phase diagram and a novel oscillating phase near EPs, with implications for magnetic nano-oscillators.

Contribution

It provides a theoretical analysis of the nonlinear spin dynamics near exceptional points in magnetic bilayers, linking EPs to dynamical phase transitions and oscillatory behavior.

Findings

Periodic oscillating phase emerges near EPs in antiferromagnetic bilayers.

Dissipative spin dynamics combined with external drives create complex phase diagrams.

Proposes methods to probe magnetic EPs and engineer nano-oscillators.

Abstract

One of the most fascinating and puzzling aspects of non-Hermitian systems is their spectral degeneracies, i.e., exceptional points (EPs), at which both eigenvalues and eigenvectors coalesce to form a defective state space. While coupled magnetic systems are natural hosts of EPs, the relation between the linear and nonlinear spin dynamics in the proximity of EPs remains relatively unexplored. Here we theoretically investigate the spin dynamics of easy-plane magnetic bilayers in the proximity of exceptional points. We show that the interplay between the intrinsically dissipative spin dynamics and external drives can yield a rich dynamical phase diagram. In particular, we find that, in antiferromagnetically coupled bilayers, a periodic oscillating dynamical phase emerges in the region enclosed by EPs. Our results not only offer a pathway for probing magnetic EPs and engineering magnetic nano-oscillators with large-amplitude oscillations, but also uncover the relation between exceptional points and dynamical phase transitions in systems displaying non-linearities.