James Hone, Columbia University
Approaching the Intrinsic Limit in Transition Metal Dichalcogenide van der Waals Heterostructures
Written by Tomojit Chowdhury
Disorders, both external and internal, in two-dimensional (2D) transition metal dichalcogenides (TMDs) are critical to the study of the intrinsic behavior of 2D TMDs. Devices made from TMD crystals containing significant disorders with defect density on the order of 1013/cm2, show low quantum yield and carrier mobility. James Hone of Columbia University introduced a new growth technique, flux synthesis, that was shown to produce 2D TMD crystals with 2-3 orders of magnitude lower defect density. Materials obtained by this method exhibited increased photoluminescence. Most importantly, the Hone group was able to observe bright trionic (trion: a localized quasi-particle consisting of three charged particles, which have a lifetime on the order of 10s of picoseconds) emission, with average trion-lifetime of 250 ps, demonstrating the first known measurement of intrinsic trion lifetime. The last part of his talk was focused on Moiré superlattices created by stacking and twisting 2D tungsten diselenide (WSe2) layered structures, implicating superconductive states, which was observed in twisted bilayer graphene structures by the Jarillo-Herrero Group at MIT.