Hyperbolic plasmon modes in tilted Dirac cone phases of borophene

TL;DR

This paper investigates hyperbolic plasmon modes in two phases of borophene with tilted Dirac cones, revealing their strong confinement, anisotropic properties, and potential for broadband plasmonic applications.

Contribution

It provides the first detailed analysis of hyperbolic plasmon modes in borophene phases with tilted Dirac cones, highlighting their unique optical and electronic properties.

Findings

Two hyperbolic regimes identified, one in the visible range.

Borophene supports low-loss hyperbolic Dirac plasmon modes.

High anisotropy and carrier density enhance plasmon confinement.

Abstract

Hyperbolic materials are receiving significant attention due to their ability to support electromagnetic fields with arbitrarily high momenta and, hence, to achieve very strong light confinement. Here, based on first-principles calculations and many-body perturbation theory, we explore the characteristic of two-dimensional plasmon modes and its hyperbolic properties for two phases of single layer boron hosting tilted Dirac cone, namely, the $hr$-$sB$ and $8Pmmn$ borophene. In-plane anisotropy in borophene is manifested in the structural, electronic, vibrational and optical properties. We find two hyperbolic regimes for both phases of borophene, where the high-energy one is located in the visible range. The $hr$-$sB$ borophene is characterised with an intrinsic high carrier density and it supports strong hyperbolic plasmon modes in the visible part of the spectrum. The $8Pmmn$ borophene, on the other hand, resembles the prototypical Dirac material graphene, and upon carrier doping acquires anisotropic Dirac plasmons in the mid-infrared. We have also investigated the impact of the electron-phonon coupling and Landau damping on these hyperbolic plasmon modes. Our results show that borophene, having high anisotropy, intrinsic high carrier concentration, low-loss hyperbolic Dirac plasmon modes, and high confinement can represent a promising candidate for low-loss broad band surface plasmon polariton devices.