Epsilon-Near-Zero Response and Tunable Perfect Absorption in Weyl Semimetals

TL;DR

This paper theoretically investigates the electromagnetic properties of Weyl semimetals, revealing tunable epsilon-near-zero responses and perfect absorption capabilities through material and geometric parameter adjustments.

Contribution

It introduces an anisotropic permittivity tensor for Weyl semimetals and demonstrates how tilts and tuning parameters enable control over epsilon-near-zero behavior and absorption.

Findings

Epsilon-near-zero response can be achieved in Weyl semimetals with appropriate tilts.

The loss in the medium can be tuned from lossless to dissipative.

Devices can be designed for perfect electromagnetic absorption over wide angles.

Abstract

We theoretically study the electromagnetic response of type-I and type-II centrosymmetric Weyl semimetals. We derive an anisotropic permittivity tensor with off-diagonal elements to describe such gyrotropic media. Our findings reveal that for appropriate Weyl cones tilts, the real part of the transverse component of the permittivity can exhibit an epsilon-near-zero response. The tilt parameter can also control the amount of loss in the medium, ranging from lossless to dissipative when transitioning from type-I to type-II. Similarly, by tuning either the frequency of the electromagnetic field or the chemical potential in the system, an epsilon-near-zero response can appear as the permittivity of the Weyl semimetal transitions between positive and negative values. Employing the obtained permittivity tensor, we consider a setup where the Weyl semimetal is deposited on a perfect conductive substrate and study the refection and absorption characteristics of this layered configuration. We show that by choosing the proper geometrical and material parameters, devices can be created that perfectly absorb electromagnetic energy over a wide angular range of incident electromagnetic waves.