Long-range self-hybridized exciton polaritons in two-dimensional Ruddlesden-Popper perovskites

TL;DR

This paper demonstrates strong exciton-photon coupling in 2D Ruddlesden-Popper perovskite layers, revealing self-hybridized exciton polaritons with high efficiency and low loss at room temperature, useful for photonic applications.

Contribution

It provides the first evidence of self-hybridization of exciton polaritons in layered perovskite crystals, combining experimental spectroscopy and simulations.

Findings

Observation of cavity mode bending indicating polariton formation

Thickness-dependent splitting of excitonic resonance

Propagation of in-plane polaritonic modes with high efficiency

Abstract

Lead halide perovskites have emerged as platforms for exciton-polaritonic studies at room temperature thanks to their excellent photoluminescence efficiency and synthetic versatility. In this work we find proof of strong exciton-photon coupling in cavities formed by the layered crystals themselves, a phenomenon known as self-hybridization effect. We use multi-layers of high quality Ruddlesden-Popper perovskites in their 2D crystalline form, benefitting from their quantum-well excitonic resonances and the strong Fabry-Perot cavity modes resulting from the total-internal-reflection at their smooth surfaces. Optical spectroscopy reveals bending of the cavity modes typical for exciton-polariton formation, and photoluminescence spectroscopy shows thickness dependent splitting of the excitonic resonance. Strikingly, local optical excitation with energy below the excitonic resonance of the flakes in photoluminescence measurements unveils coupling of light to in-plane polaritonic modes with directed propagation. These exciton-polaritons exhibit high coupling efficiencies and extremely low loss propagation mechanisms which is confirmed by finite difference time domain simulations. We therefore prove that mesoscopic 2D Ruddlesden-Popper perovskites flakes represent an effective but simple system to study the rich physics of exciton-polaritons at room temperature.