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Valley selective condensation and expansion of exci- ton-polaritons based on MoSe2 monolayer crystals

Jeudi 8 novembre 2018 11:00 - Duree : 1 heure
Lieu : Salle du bâtiment accueil, CEA - 17 rue des Martyrs - Grenoble

Orateur : Christian SCHNEIDER

Condensation of bosons into a macroscopic quantum state belongs to the most intriguing phenomena in nature, which becam e accessible in open-dissipative, exciton-based solid-state systems at elevated temperatures. Semiconducting monolayer crystals have emerged as a new platform for studies of strongly bound excitons and exciton-polaritons [1] in ultimately thin materials. We discuss the formation of a bosonic condensate driven by excitons hosted in an atomically thin layer of MoSe2, strongly coupled to light in a solid-state resonator [2]. Polariton condensation manifests by a superlinear increase of emission intensity from the hybrid polaritons. The mode experiences a collapse of the emission linewidth, a core sign of temporal coherence. With increasing pump power, we observe a blueshift of our resonance which originates from particle interaction with free excitons in the uncondensed reservoir states. Importantly, we observe a significant spin-polarization in the injected polariton condensate, a clear sign for valley-selective condensation in our crystal. In turn, high fidelity spin-selective, as well as valley-coherent injection of valley exciton-polaritons is demonstrated via resonant, non-linear spectroscopy. In contrast to previous experiments based on excitons in bare MoSe2 monolayer crystals, valley polarization and coherence can be retained to a very high degree the MoSe2 polariton-system. As a consequence, valley selective polariton currents emerge in the expanding polariton cloud, a manifestation of the optical valley Hall effect in the hybrid light-matter system.

[1] C. Schneider et al. Nature Communications 9, 2695 (2018) [2] M. Waldherr et al. Nature Communications 9, 3286 (2018)

Contact : johann.coraux@neel.cnrs.fr

Discipline évènement : (Physique)
Entité organisatrice : (Institut Néel / QUEST)
Nature évènement : (Séminaire)
Site de l'évènement : Site CEA sans badge requis

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