Sommaire:

Monolayers of semiconducting transition metal dichalcogenides are direct band gap semiconductors for which the direct band gap is located in the two inequivalent K and K' valleys. Because of the lack of inversion symetry and of the large spin orbit interaction, the spin and valley degrees of freedom are strongly coupled and a particular valley exciton population can be initialized using circularly polarized light excitation. As two dimensional materials, monolayers can be stacked on top of one another in the form of van der waals heterostructures to create artifical materials. Heterostructure of monolayer of TMD encapsulated in hBN offer a rich plateform to study the properties of 2D excitons.

In this talk, I will describe optical properties of bright and dark excitons in monolayers of TMD encapsulated in hexagonal boron nitride. Because of their 2D nature, excitons in monolayers of TMDs arze tighly bound and their propertie are strongly influenced by the dielectric environment. The relevent spectroscopic signature of such modifications is inscribed in their excitation spectrum and I will present a model to describe such influence. Dark excitons are activated by magnetic fields applied in different configurations. The exchange interaction mixes dark excitons in the two valleys and I will show how this mixing can be monitored by external magbetic fields.

Pour plus d'informations, merci de contacter Cassabois G.