Nonreciprocal and non-Hermitian material response inspired by semiconductor transistors

TL;DR

This paper introduces a new class of bulk materials inspired by semiconductor transistors that exhibit nonreciprocal, non-Hermitian electromagnetic responses, enabling energy dissipation or generation and surpassing traditional isolators.

Contribution

It proposes a novel paradigm to break electromagnetic reciprocity in bulk nonlinear materials using static electric bias, inspired by transistor operation.

Findings

Material nonlinearities with static bias lead to non-Hermitian permittivity tensors.

Designed an electromagnetic isolator surpassing conventional Faraday isolators.

Natural media may exhibit similar responses in nonequilibrium conditions.

Abstract

Here, inspired by the operation of conventional semiconductor transistors, we introduce a novel class of bulk materials with nonreciprocal and non-Hermitian electromagnetic response. Our analysis shows that material nonlinearities combined with a static electric bias may lead to a linearized permittivity tensor that lacks the Hermitian and transpose symmetries. Remarkably, the material can either dissipate or generate energy, depending on the relative phase of the electric field components. We introduce a simple design for an electromagnetic isolator based on an idealized "MOSFET-metamaterial" and show that its performance can in principle surpass conventional Faraday isolators due to the material gain. Furthermore, it is suggested that analogous material responses may be engineered in natural media in nonequilibrium situations. Our solution determines an entirely novel paradigm to break the electromagnetic reciprocity in a bulk nonlinear material using a static electric bias.