jz0c00169_si_001.pdf (4.3 MB)
Evidence for the Dominance of Carrier-Induced Band Gap Renormalization over Biexciton Formation in Cryogenic Ultrafast Experiments on MoS2 Monolayers
journal contribution
posted on 2020-03-20, 16:35 authored by Ryan E. Wood, Lawson T. Lloyd, Fauzia Mujid, Lili Wang, Marco A. Allodi, Hui Gao, Richard Mazuski, Po-Chieh Ting, Saien Xie, Jiwoong Park, Gregory S. EngelTransition-metal
dichalcogenides (TMDs) such as MoS2 display promising electrical
and optical properties in the monolayer
limit. Due to strong quantum confinement, TMDs provide an ideal environment
for exploring excitonic physics using ultrafast spectroscopy. However,
the interplay between collective excitation effects on single excitons
such as band gap renormalization/exciton binding energy (BGR/EBE)
change and multiexciton effects such biexciton formation remains poorly
understood. Using two-dimensional electronic spectroscopy, we observe
the dominance of single-exciton BGR/EBE signals over optically induced
biexciton formation. We make this determination based on a lack of
strong PIA features at T = 0 fs in the cryogenic
spectra. By means of nodal line slope analysis, we determine that
spectral diffusion occurs faster than BGR/EBE change, indicative of
distinct processes. These results indicate that at higher sub-Mott
limit fluences, collective effects on single excitons dominate biexciton
formation.