# Giant Non-reciprocity Near Exceptional Point Degeneracies

## TL;DR

This paper demonstrates that gyrotropic structures with balanced gain and loss exhibit giant non-reciprocity near exceptional point degeneracies, confirmed through numerical and circuit modeling, with potential universal applications across wave systems.

## Contribution

It reveals a giant non-reciprocal effect near exceptional points in non-Hermitian gyrotropic systems, combining theoretical, numerical, and circuit analyses.

## Key findings

- Non-reciprocal transport exceeds 90dB in microwave experiments
- Giant non-reciprocity occurs near exceptional point degeneracies
- Universal phenomenon potentially applicable to various wave systems

## Abstract

We show that gyrotropic structures with balanced gain and loss that respect anti-linear symmetries exhibit a giant non-reciprocity at the so-called exact phase where the eigenfrequencies of the isolated non-Hermitian set-up are real. The effect occurs in a parameter domain near an exceptional point (EP) degeneracy, where mode-orthogonality collapses. The theoretical predictions are confirmed numerically in the microwave domain, where a non-reciprocal transport above 90dB is demonstrated, and are further verified using lump-circuitry modeling. The analysis allows us to speculate the universal nature of the phenomenon for any wave system where EP and gyrotropy can co-exist.