Optical properties of dark excitons in transition metal dichalcogenides (TMDs) have been received lots of attention due to its significant role in fundamental properties of exciton physics. Here, we demonstrate up-converted photoluminescence (PL) in few-layer WSe2 through exciton-exciton annihilation of intervalley dark excitons. WSe2 was mechanically exfoliated onto silicon substrates with 285-nm-thick SiO2 using a dry transfer technique. We performed low-temperature micro-PL measurement, showing a resonant PL emission when up-converted excitons overlap the band-nesting region. We also show that the up-conversion mechanism in few-layer WSe2 is exciton-exciton annihilation, which is different in contrast to the Auger recombination in bulk WSe2. The finding is found to be universal among few-layer TMDs, including MoS2, MoSe2, and WS2.
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.