Polaritons in layered 2D materials

TL;DR

This paper reviews recent advances in polaritonic excitations in layered 2D materials, highlighting their unique optical properties, experimental progress, and potential applications across a broad spectral range.

Contribution

It provides a comprehensive survey of polaritonic modes in 2D materials, summarizing experimental findings, optical characteristics, and future application prospects.

Findings

Graphene plasmon-polaritons are electrically tunable and highly confined.

hBN exhibits hyperbolic phonon-polaritons with high quality factors.

TMDs support exciton-polaritons with large binding energies.

Abstract

In recent years, enhanced light-matter interactions through a plethora of dipole-type polaritonic excitations have been observed in two-dimensional (2D) layered materials. In graphene, electrically tunable and highly confined plasmon-polaritons were predicted and observed, opening up opportunities for optoelectronics, bio-sensing and other mid-infrared applications. In hexagonal boron nitride (hBN), low-loss infrared-active phonon-polaritons exhibit hyperbolic behavior for some frequencies, allowing for ray-like propagation exhibiting high quality factors and hyperlensing effects. In transition metal dichalcogenides (TMDs), reduced screening in the 2D limit leads to optically prominent excitons with large binding energy, with these polaritonic modes having been recently observed with scanning near field optical microscopy (SNOM). Here, we review recent progress in state-of-the-art experiments, survey the vast library of polaritonic modes in 2D materials, their optical spectral properties, figures-of-merit and application space. Taken together, the emerging field of 2D material polaritonics and their hybrids provide enticing avenues for manipulating light-matter interactions across the visible, infrared to terahertz spectral ranges, with new optical control beyond what can be achieved using traditional bulk materials.