Possible realization of hyperbolic plasmons in a few-layered rhenium disulfide

TL;DR

This study demonstrates that the naturally anisotropic distorted-1T phase of ReS$_2$ can host hyperbolic plasmons in the ultraviolet, with the HP window controlled by layer number and uniaxial strain. Using self-consistent QS$G\widehat{W}$-BSE calculations, the authors show ML ReS$_2$ lacks HP, while bilayer and bulk variants exhibit UV hyperbolic regions whose width and damping depend on direction and strain. The work highlights a route to tunable, layer-dependent UV plasmonics in a naturally occurring 2D material, with potential implications for nanoscale optoelectronics and photonics. The findings emphasize the role of strong dielectric anisotropy in realizing hyperbolic behavior without engineered metamaterials, and suggest practical pathways for device integration via strain engineering.

Abstract

The in-plane structural anisotropy in low-symmetric layered compound rhenium disulfide ($\text{ReS}_2$) makes it a candidate to host and tune electromagnetic phenomena specific for anisotropic media. In particular, optical anisotropy may lead to the appearance of hyperbolic plasmons, a highly desired property in optoelectronics. The necessary condition is a strong anisotropy of the principal components of the dielectric function, such that at some frequency range, one component is negative and the other is positive, i.e., one component is metallic, and the other one is dielectric. Here, we study the effect of anisotropy in $\text{ReS}_2$ and show that it can be a natural material to host hyperbolic plasmons in the ultraviolet frequency range. The operating frequency range of the hyperbolic plasmons can be tuned with the number of $\text{ReS}_2$ layers.

Figures (4)

• Figure 1: The ball-stick model of the bulk distorted 1T diamond-chain $\text{ReS}_2$ obtained using VESTA software momma2011vesta is presented. Top view (Fig.1(a)) and side view (Fig.1(b))of the distorted 1T-$\text{ReS}_2$; Re atoms are in red and S atoms are in green. The black outline shows the unit cell used for the calculation. The Re chain is along b direction. Brillouin zone (bottom) of the corresponding hexagonal lattice with lines connecting high-symmetry points $\Gamma$-K1-K2-M2-$\Gamma$-K4-K3-M2-$\Gamma$. $a^*$ and $b^*$ denote reciprocal lattice vectors.
• Figure 2: QSG$\widehat{W}$ band structures (with spin-orbit coupling) with contributions from Re (Red) and S (green). The nature of the band gap is indirect for all the variants of $\text{ReS}_2$ with values, 2.66eV for ML (left), 2.3eV for BL (center) and 1.7eV for bulk (right).
• Figure 3: Real part($\epsilon_1$) of the dielectric response (top row) and imaginary part (bottom row) along $x$ and $y$ direction for ML (left), BL (center) and bulk (right). The vertical dashed line marks the plasmonic frequency range, where $\epsilon_1^{xx}(\omega) \times \epsilon_1^{yy}(\omega) < 0$.
• Figure 4: The product of the real part of the dielectric response along X($\epsilon_1^{xx}(\omega)$) and Y($\epsilon_1^{yy}(\omega)$) direction for ML(left),BL(center) and Bulk(right). The vertical dashed line marks the frequency range in which the product is negative. This frequency range is hyperbolic plasmonic frequency range.