Magnetic-field-tunable cyclotron hyperbolic polaritons

TL;DR

This paper predicts a new class of hyperbolic polaritons generated by magnetic-field-induced cyclotron motion in high-mobility semimetals, enabling tunable nanophotonic applications.

Contribution

It introduces cyclotron motion as a novel mechanism for creating hyperbolic polaritons, expanding the understanding of magnetically tunable nanophotonics.

Findings

Magnetic fields induce hyperbolic dielectric environments in semimetals.

Cyclotron resonance frequency controls the transition from metallic to insulating response.

Real-space visualization of these modes is possible via terahertz near-field nanoscopy.

Abstract

Hyperbolic polaritons are conventionally associated with structural anisotropy or phononic Reststrahlen bands. Here, we predict a new class of hyperbolic polaritons arising from magnetic-field-induced cyclotron motion of charge carriers. When a perpendicular magnetic field is applied to high-mobility semimetals, the cyclotron response drives the in-plane dielectric function from metallic- to insulating-like below the cyclotron resonance frequency, while the out-of-plane response remains metallic. This anisotropy creates a hyperbolic dielectric environment that supports field-tunable hyperbolic polaritons. We develop a comprehensive theoretical framework incorporating coupling to other collective excitations and show that these modes can be directly visualized in real space via terahertz near-field nanoscopy. Our work identifies cyclotron motion as a new route to hyperbolic polaritons and establishes a versatile platform for magnetically programmable nanophotonics.