Ultrastrong Coupling of Band-Nested Excitons in Few-Layer Molybdenum Disulphide

TL;DR

This paper demonstrates ultrastrong light-matter coupling in few-layer molybdenum disulphide by achieving a significant Rabi splitting with surface plasmon polaritons, advancing the potential for quantum coherent processes in 2D materials.

Contribution

It introduces a new approach using the large oscillator strength of the C exciton in FL-MoS2 to achieve ultrastrong coupling at room temperature.

Findings

Achieved a 293 meV Rabi splitting in FL-MoS2 with surface plasmon polaritons.

The coupling strength is approximately 11% of the exciton energy, entering the ultrastrong regime.

Demonstrated potential for quantum coherent processes in CMOS-compatible 2D materials.

Abstract

The two-dimensional transition-metal dichalcogenides (2D TMDCs) are an intriguing platform for studying light-matter interactions because they combine the electronic properties of conventional semiconductors with the optical resonances found in organic systems. However, the coupling strengths demonstrated in strong exciton-polariton coupling remain much lower than those found in organic systems. In this paper, we take on a new approach by utilizing the large oscillator strength of the above-band gap C exciton in few-layer molybdenum disulphide ($\text{FL-MoS}_2$). We show a k-space Rabi splitting of 293 meV when coupling $\text{FL-MoS}_2$ C excitons to surface plasmon polaritons at room temperature. This value is 11% of the uncoupled exciton energy (2.67 eV or 464 nm), ~2x what is typically seen in the TMDCs, placing the system in the ultrastrong coupling regime. Our results take a step towards finally achieving the efficient quantum coherent processes of ultrastrong coupling in a CMOS-compatible system -- the 2D TMDCs -- in the visible spectrum.