Highly Confined In-plane Exciton-Polaritons in Monolayer Semiconductors

TL;DR

This paper reports the discovery of a new type of in-plane exciton-polariton in monolayer TMDs, demonstrating large confinement and specific conditions for excitation, advancing 2D polariton research.

Contribution

It introduces the 2D in-plane exciton-polariton (2DEP), a novel polariton supported on monolayer TMDs, with detailed experimental conditions and comparison to surface plasmons.

Findings

2DEP exhibits over two orders-of-magnitude larger wavelength confinement than SPPs.

Specific conditions involve encapsulation with hBN and cryogenic cooling.

Proposed experimental configurations for observing 2DEP.

Abstract

2D materials support unique excitations of quasi-particles that consist of a material excitation and photons called polaritons. Especially interesting are in-plane propagating polaritons which can be confined to a single monolayer and carry large momentum. In this work, we report the existence of a new type of in-plane propagating polariton, supported on monolayer transition-metal-dicalcogonide (TMD) in the visible spectrum, which has not yet been observed. This 2D in-plane exciton-polariton (2DEP) is described by the coupling of an electromagnetic light field with the collective oscillations of the excitons supported by monolayer TMDs. We expose the specific experimental conditions required for the excitation of the 2DEP and show that these can be created if the TMD is encapsulated with hexagonal-boron-nitride (hBN) and cooled to cryogenic temperatures. In addition, we compare the properties of the 2DEPs with those of surface-plasmons-polaritons (SPPs) at the same spectral range, and find that the 2DEP exhibit over two orders-of-magnitude larger wavelength confinement. Finally, we propose two configurations for the possible experimental observation of 2DEPs.