# Observation of anti-PT symmetry phase transition in the magnon-cavity-magnon coupled system

## TL;DR

This paper experimentally demonstrates anti-PT symmetry phase transition in a magnon-cavity-magnon system using dissipative coupling via a microwave cavity, revealing level attraction and opening new research avenues.

## Contribution

It introduces a novel experimental realization of anti-PT symmetry in a magnon system with dissipative coupling, utilizing a new magnon-readout method.

## Key findings

- Demonstrated anti-PT symmetry phase transition in a magnon-cavity system.
- Observed counterintuitive level attraction process.
- Established a new platform for studying anti-PT symmetry properties.

## Abstract

As the counterpart of PT symmetry, abundant phenomena and potential applications of anti-PT symmetry have been predicted or demonstrated theoretically. However, experimental realization of the coupling required in the anti-PT symmetry is difficult. Here, by coupling two YIG spheres to a microwave cavity, the large cavity dissipation rate makes the magnons coupled dissipatively with each other, thereby obeying a two-dimensional anti-PT Hamiltonian. In terms of the magnon-readout method, a new method adopted here, we demonstrate the validity of our method in constructing an anti-PT system and present the counterintuitive level attraction process. Our work provides a new platform to explore the anti-PT symmetry properties and paves the way to study multi-magnoncavity-polariton systems.