Here, we demonstrate up-conversion photoluminescence of optically forbidden (dark) excitons in few-layer transition metal dichalcogenides. Transition metal dichalcogenides were mechanically exfoliated onto sapphire substrates using a dry transfer technique.
We show that the resonance between up-converted excitons and the bright exciton state at Γ valley results in a strongly enhanced photoluminescence, evidenced by temperature, layer and excitation dependent photoluminescence measurements.
We attribute this process to exciton-exciton annihilation of dark excitons, which is in stark contrast to the Auger recombination in bulk counterparts, based on the power-dependent measurement. This novel radiative pathway in two-dimensional semiconducting materials may pave the way to explore fundamental properties and applications of dark excitons.
About the presenter
Yi-Hsen Chen is a PhD student at Monash University with CI Michael Fuhrer. He researches Bose-Einstein condensates using devices constructed using 2D materials, as part of FLEET’s Research Theme 2, Exciton Superfluids.