Maximal Violation of Kirchhoff's Law in Planar Heterostructures

TL;DR

This paper demonstrates that pattern-free dielectric heterostructures with a resonant mode can maximally violate Kirchhoff's law, expanding possibilities beyond nonreciprocal microstructured materials.

Contribution

It introduces a new mechanism for violating Kirchhoff's law using simple heterostructures with resonant modes, without requiring patterned nonreciprocal materials.

Findings

Resonant modes in dielectric spacers enable violation of Kirchhoff's law.

Minimal dielectric requirements are identified for this effect.

The approach is compatible with existing materials.

Abstract

Violating Kirchhoff's law has so far required nonreciprocal materials patterned in microstructures. In these configurations, the excitation of a guided or polaritonic mode that lies outside the light cone, often via gratings, was a requirement. Here, we describe how nonreciprocity manifests itself in pattern-free heterostructures. We demonstrate that a resonant mode in a dielectric spacer separating a nonreciprocal film from a back-reflector suffices to maximally violate Kirchhoff's law, and identify the minimal dielectric requirements for such functionality, which are satisfied by currently available materials.