2D semiconductors: a platform for ultrafast photonics

Layered materials consist of crystalline sheets with strong in-plane covalent bonds and weak van der Waals out-of-plane interactions. These materials can be easily exfoliated to a single layer, obtaining 2D materials with radically novel physico-chemical characteristics compared to their bulk counterparts. 2D semiconductors exhibit very strong light-matter interaction and exceptionally intense and ultrafast nonlinear optical response, enabling a variety of applications in optoelectronics and photonics. Furthermore, stacking 2D materials into heterostructures (HS) offers unlimited possibilities to design new materials tailored for applications

This talk will review our recent studies on the ultrafast non-equilibrium optical response of transition metal dichalcogenides (TMDs) and their HS. Using high time resolution ultrafast transient absorption (TA) spectroscopy, we monitor the ultrafast onset of exciton formation in TMDs and the dynamics of strongly coupled phonons. Using helicity resolved TA spectroscopy we time-resolve and control intravalley spin-flip processes. In HS of TMDs we time-resolve ultrafast interlayer hole transfer and interlayer exciton formation processes. We also show that strong exciton nonlinear interactions can lead to a complete quenching of the Rabi splitting in TMD-based microcavities.

Speaker: Giulio Cerullo, Politecnico di Milano, Italy