Optically tunable giant bandgap renormalization in atomically thin transition metal dichalcogenides*

Two-dimensional transition metal dichalcogenides are emerging opto-electronic materials that feature strong many-body coulomb interactions due to reduced dielectric screening and quantum confinement. These many-body interactions can be strongly modified by optically injecting large number of carriers, which provides a method to engineer the excited state optical response. Here, we explore new insights into excited state properties in monolayer CVD grown MoS₂ by implementing spectrally and temporarily resolved ultrafast pump-probe transient absorption spectroscopy. Our pump fluence dependent study reveals a drastic change in the optical response over a wide spectral region, which is manifestation of giant bandgap renormalization of around 1100 meV, one order higher than the conventional semiconductors. Further, we observe a transient redshift followed by an anomalous blueshift of exciton energy with an increase in carrier density and modeled using a phenomenological framework similar to Lennard-Jones potential with modified exponents. Our experimental findings suggest that MoS₂ can be a promising material for solid-state technologies by precise and efficient manipulation of electrons in the excited state.