Regular Article

Experimental study of the high-order exceptional points in a four-state non-Hermitian microwave meta-atoms system

¹ College of Science, University of Shanghai for Science and Technology, Shanghai 200093, P.R. China
² Shanxi Provincial Key Laboratory of Microstructure Electromagnetic Functional Materials, Shanxi Datong University, Datong 037009, P.R. China

^* e-mail: dyq@usst.edu.cn

Received: 11 August 2023
Received in final form: 4 October 2023
Accepted: 9 October 2023
Published online: 6 November 2023

Abstract

Non-Hermitian degeneracies, also known as exceptional points, have recently attracted increased attention due to their enhanced sensitivity and distinct topological features. We realize the non-Hermitian system experimentally using four coupled microwave meta-atoms with asymmetric losses. By tuning eigenfrequencies and dissipative losses of meta-atoms, we obtain both theoretically and experimentally that multiple EPs can collide and merge, leading to higher-order singularities much richer than those seen in two-state systems. These findings are expected to enrich our understanding of EP physics and provide a robust foundation for the exploration of high-order EP applications.