Xavier Marie, Institute National des Sciences Appliquées

Title: Exciton and valley dynamics in 2D semiconductors based on transition metal dichalcogenides
Session: Monday 5 October, 15:45


The spectacular progress in controlling the electronic properties of graphene has triggered research in alternative atomically thin two-dimensional crystals. Monolayers (ML) of transition-metal dichalcogenides such as MoS2 have emerged as very promising nanostructures for optical and electronic applications for mainly two reasons.

First, the indirect bulk semiconductor MoS2 becomes direct when thinned to 1ML, resulting in efficient optical absorption and emission. Second, inversion symmetry breaking (usually absent in graphene) together with the large spin-orbit interaction leads to a coupling of carrier spin and k-space valley physics, i.e., the circular polarization (σ+ or σ−) of the absorbed or emitted photon can be directly associated with selective carrier excitation in one of the two nonequivalent k valleys (K+ or K−, respectively).

In this talk I will give an overview of the physical properties of 2D semiconductors based on Transition Metal Dichalcogenides (MoS2, MoSe2, WS2, WSe2) : band structure, exciton effects, spin and valley dynamics.



Xavier Marie is Professor at the National Institute of Applied Sciences (INSA- University of Toulouse). He was a member of the French University Academy in 2005-2010 ("Institut Universitaire de France"). He was Director of the Laboratory of Physics and Chemistry of Nano-Objects (LPCNO ; UMR 5215) untill 2011. After a Master of Science at the University of Essex (UK) and a French engineering Degree he received his PhD degree in 1991 in Toulouse working on Optical Spectroscopy of quantum wells. He has worked for about 20 years on ultrafast optical spectroscopy of low dimensional semiconductor structures (quantum wells, quantum dots). His main present interest is the optical and spin coherence in semiconductor nanostructures and band structure engineering of semiconductors for optical telecommunication devices. Xavier Marie is the author or co-author of about 170 papers and communications in refereed journals (WOS) and 7 book chapters. He gave 60 invited talks in International Conferences and 11 lectures in International Summer Schools. He is a regular expert and member of panels for EPSRC (United Kingdom), DFG (Germany), IOP (China), ANR (France), etc...


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