Itai Epstein: Extremely Efficient Light-Exciton Interaction in a Monolayer Semiconductor Van der Waals Heterostructure Cavity

posted 27 Jun 2019, 09:20 by info admin   [ updated 28 Jun 2019, 02:48 ]
ICFO - The Institute of Photonic Sciences, Castelldefels 08860, Barcelona, Spain

Semiconductor two-dimensional materials, such as transition-metal-dichalcogenides (TMDs), exhibit extraordinary optoelectronic properties due to their unique band structure and the ability to tune their charge carrier density. The combination of a direct bandgap together with large exciton binding energies leads to an optical response that is completely dominated by the supported excitons in these materials.  
In this work, we demonstrate a TMD-based high quality Van der Waals heterostructure cavity, in which the achieved interaction strength is unitary and can be controlled both electrically and optically. Figure 1 shows the non-trivial behavior of the temperature dependent interaction strength via the FWHM of the exciton supported by the monolayer TMD.  We develop a theoretical framework to describe the light-exciton-cavity interaction, which fully supports the experimental results.  
The heterostructure cavity also enables the excitation of a large photo-excited excitonic population while still maintaining low optical power. This high density of excitons allows the observation of high order excitonic complexes, with ultra-low continuous-wave (CW) laser power excitation down to few nW.  Finally, we show that by modifying the structure of the cavity we are able to fully tailor the interaction strength from 0-100%.  
This enhanced light-exciton interaction paves the way to possible polaritonic condensation in monolayer semiconductors and excitonic optoelectronic devices based on 2D semiconductors. 

Itai Epstein is a postdoctoral researcher at the group of Prof. Frank Koppens at ICFO - The institute of photonic sciences, Barcelona, Spain. His postdoctoral research is devoted to studying light-matter interaction in 2D materials, such as graphene, transition-metal-dichalcogenides (TMDs), and hexagonal-boron-nitride (hBN). In particular, he is working on experimentally exposing new polaritonic phenomena in these materials, and new methods to achieve strong light-2D matter interaction. His PhD research, under the supervision of Prof. Ady Arie, at Tel Aviv University, focused on the investigation of surface plasmon waves in the scope of fundamental wave phenomena, and his M.Sc research, under the supervision of Prof. Yossi Rosenwaks, at Tel Aviv University, focused on the investigation of electronic transport properties of thin film transistors.