Infrared Plasmons Propagate through a Hyperbolic Nodal Metal

TL;DR

This paper demonstrates the first observation of propagating hyperbolic plasmons in a layered nodal-line semimetal, enabled by its unique electronic structure that suppresses losses and enhances plasmonic response.

Contribution

It reports the experimental realization of hyperbolic waveguiding in a layered nodal-line semimetal, revealing a new class of low-loss infrared plasmonic materials.

Findings

Propagating hyperbolic waves observed in ZrSiSe

Nodal electronic structures suppress interband losses

Enhanced plasmonic response enables infrared mode propagation

Abstract

Metals are canonical plasmonic media at infrared and optical wavelengths, allowing one to guide and manipulate light at the nano-scale. A special form of optical waveguiding is afforded by highly anisotropic crystals revealing the opposite signs of the dielectric functions along orthogonal directions. These media are classified as hyperbolic and include crystalline insulators, semiconductors and artificial metamaterials. Layered anisotropic metals are also anticipated to support hyperbolic waveguiding. Yet this behavior remains elusive, primarily because interband losses arrest the propagation of infrared modes. Here, we report on the observation of propagating hyperbolic waves in a prototypical layered nodal-line semimetal ZrSiSe. The observed waveguiding originates from polaritonic hybridization between near-infrared light and nodal-line plasmons. Unique nodal electronic structures simultaneously suppress interband loss and boost the plasmonic response, ultimately enabling the propagation of infrared modes through the bulk of the crystal.