Nonreciprocal singularities dominated by the dissipative photon-magnon coupling in non-Hermitian systems

TL;DR

This paper explores nonreciprocal singularities in an open cavity magnonic system, revealing how dissipative photon-magnon coupling leads to exceptional points and bound states in the continuum, with experimental realization and theoretical understanding.

Contribution

It demonstrates the experimental realization of two distinct nonreciprocal singularities driven by dissipative coupling in a magnon-photon system, supported by pseudo-Hermitian theory.

Findings

Identification of exceptional points on the exceptional surface.

Discovery of bound states in the continuum above the exceptional surface.

Experimental demonstration of nonreciprocity and selectivity in the system.

Abstract

We investigated the magnon-photon coupling in an open cavity magnonic system, which leads to two different nonreciprocal singularities dominated by the dissipative coupling. One type of singularity is the exceptional point, which is just on the exceptional surface in parameter space. The other type of singularity is the bound state in the continuum discovered in the level-attraction-like coupling, which is above the exceptional surface. In experiment, we realized the two different singularities with nonreciprocity and selectivity in an open cavity magnonic system with suitable dissipation rating. Our results can be understood well with the pseudo-Hermitian theory of magnon-polariton system.