Tellegen responses in metamaterials

TL;DR

This paper reports the experimental realization of Tellegen metamaterials in the microwave range, demonstrating significant effective Tellegen parameters and potential applications in nonreciprocal photonics and axion physics research.

Contribution

It presents the first practical implementation of Tellegen metamaterials with large effective parameters, linking metamaterial design to axion physics and nonreciprocal device development.

Findings

Observed Kerr rotation in reflected waves indicating Tellegen response

Effective Tellegen parameter is several orders of magnitude larger than natural materials

Demonstrated potential for nonreciprocal photonic devices

Abstract

Tellegen medium has long been a topic of debate, with its existence being contested over several decades. It was first proposed by Tellegen in 1948 and is characterized by a real-valued cross coupling between electric and magnetic responses, distinguishing it from the well-known chiral medium that has imaginary coupling coefficients. Significantly, Tellegen responses are closely linked to axion dynamics, an extensively studied subject in condensed matter physics. Here, we report the realization of Tellegen metamaterials in the microwave region through a judicious combination of subwavelength metallic resonators, gyromagnetic materials, and permanent magnet discs. We observe the key signature of the Tellegen response, i.e. a Kerr rotation for reflected wave, while the polarization remains the same in the transmission direction. The retrieved effective Tellegen parameter is several orders of magnitude greater than that of natural materials. Our work opens door to a variety of nonreciprocal photonic devices and may provide a platform for studying axion physics.