Observation of bosonic condensation in a hybrid monolayer MoSe2-GaAs microcavity

Abstract

Bosonic condensation belongs to the most intriguing phenomena in physics, and was mostly reserved for experiments with ultra-cold quantum gases. More recently, it became accessible in exciton-based solid-state systems at elevated temperatures. Here, we demonstrate bosonic condensation driven by excitons hosted in an atomically thin layer of MoSe2, strongly coupled to light in a solid-state resonator. The structure is operated in the regime of collective strong coupling between a Tamm-plasmon resonance, GaAs quantum well excitons, and two-dimensional excitons confined in the monolayer crystal. Polariton condensation in a monolayer crystal manifests by a superlinear increase of emission intensity from the hybrid polariton mode, its density-dependent blueshift, and a dramatic collapse of the emission linewidth, a hallmark of temporal coherence. Importantly, we observe a significant spin-polarization in the injected polariton condensate, a fingerprint for spin-valley locking in monolayer excitons. Our results pave the way towards highly nonlinear, coherent valleytronic devices and light sources.

Magnetic-field-induced splitting and polarization of monolayer-based valley exciton polaritons

“…The fragmentation of the spectrum is a strong indication of photonic disorder in our system. The monolayer extension locally confines the optical mode in our structure 24 . From the mode splitting, we can estimate an effective trapping length of ~ 6.4 µm.…”

Organic Polariton Lasing and the Weak to Strong Coupling Crossover

“…Indeed, polariton lasing does not need electronic inversion, and so it is often stated that it can provide coherent light sources with ultra-low thresholds. Polariton lasing can also occur at room temperature in appropriate materials: inorganic materials such as wide bandgap semiconductors [7-9] and two-dimensional materials [10], and the focus of this Letter, organic materials [11][12][13].Polariton condensation in organic materials prompts interesting questions regarding the mechanisms of polariton relaxation and lasing. Excitons in organic materials are Frenkel excitons -electronic excitations of a molecule or chromaphore delocalized by hopping [14].…”

Recent Progress on Exciton Polaritons in Layered Transition‐Metal Dichalcogenides

“…In a different study, hybrid Tamm‐plasmon EPs generated due to the strong coupling between excitons in GaAs quantum wells, MoSe 2 monolayer, and cavity photons were observed. Such hybrid PEPs inherit the properties of strongly interacting excitons from both GaAs quantum wells and MoSe 2 , resulting in Bose‐Einstein condensation at an elevated temperature of 4.2 K …”

“…f) Polarization‐resolved PL spectra at zero in‐plane momentum under pump power below and above the condensation threshold. f) Reproduced with permission . Copyright 2018, Springer Nature.…”

“…It was also found that Bose‐Einstein condensation enhances valley coherence of polaritons. In this case, hybrid EPs formed by strong coupling between a Tamm‐plasmon resonance, GaAs quantum well excitons, and MoSe 2 excitons were studied . Figure f plots polarization‐resolved spectra under excitation power below and above the condensation threshold.…”