Observation of two thresholds leading to polariton condensation in 2D hybrid perovskites

TL;DR

This paper reports the first observation of two distinct thresholds leading to polariton condensation in 2D hybrid perovskites, including lasing from bi-exciton states and formation of a quantum coherent state at room temperature.

Contribution

It demonstrates for the first time two threshold processes in 2D perovskites, revealing new insights into polariton condensation mechanisms in these materials.

Findings

Observation of two thresholds in 2D perovskite polariton systems

Lasing from bi-exciton states contributing to polariton population

Formation of a polariton condensate with spatial coherence

Abstract

Two dimensional (2D) perovskites are promising materials for photonic applications, given their outstanding nonlinear optical properties, ease of fabrication and versatility. In particular, exploiting their high oscillator strength, the crystalline form of 2D perovskites can be used as excitonic medium in optical microcavities, allowing for the study of their optical properties in the strong light-matter coupling regime. While polariton condensation has been observed in different materials at room temperature, here we observe for the first time two distinct threshold processes in a 2D perovskite, a material that has never shown spontaneous phase transition up to now. In particular, we demonstrate lasing from the bi-exciton state which contributes to populate the lower polariton branch and, at higher excitation powers, eventually leads to the formation of a polariton condensate. The emission linewidth narrowing and a spatial coherence over 50 x 50 um2 area are the smoking gun, the formation of a quantum coherent state in 2D hybrid perovskite. Our results not only show the formation of a polariton condensate in 2D perovskites but they are also crucial for the understanding of the physical mechanisms that leads to coherent phase transition in perovskite-based polariton microcavities.