Special seminar with Dicke fellowship candidate: Giovanni Scuri, Harvard University
Abstract: The twist degree of freedom provides a powerful tool for engineering the electrical and optical properties of van der Waals (vdW) heterostructures. In this talk, I will show how the twist angle between two layers of transition metal dichalcogenides can be used both to control the exciton spin-valley properties, and to create an array of two distinct exciton species. In the first part of the talk, I will discuss how the twist angle in a WSe2/WSe2 bilayer can be used to efficiently engineer interlayer excitons with a long-lived valley state. The valley lifetime can be tuned by more than three orders of magnitude via electrostatic doping, enabling switching of the valley polarization. In the second part of the talk, I will introduce a secondary electron microscope technique that allows for the direct imaging of the twist-induced moiré lattice. Using this technique, we directly correlate increasing moiré periodicity with the emergence of two distinct exciton species residing in alternating locations in the superlattice. Our work opens up avenues for new device schemes that exploit the valley degree of freedom, and for realizing tunable exciton arrays in twisted vdW heterostructures, with applications in quantum optoelectronics and explorations of novel many body systems.