Anomalous Stark Shift of Excitonic Complexes in Monolayer Semiconductor

Abstract

Monolayer transition metal dichalcogenide semiconductors host strongly bound twodimensional excitonic complexes, and form an excellent platform for probing manybody physics through manipulation of Coulomb interaction. Quantum confined Stark effect is one of the routes to dynamically tune the emission line of these excitonic complexes. In this work, using a high quality graphene/hBN/WS 2 /hBN/Au vertical heterojunction, we demonstrate for the first time, an out-of-plane electric field driven change in the sign of the Stark shift from blue to red for four different excitonic species, namely, the neutral exciton, the charged exciton (trion), the charged biexciton, and the defect-bound exciton. Such universal non-monotonic Stark shift with electric field arises from a competition between the conventional quantum confined Stark effect

Highly Tunable Layered Exciton in Bilayer WS2: Linear Quantum Confined Stark Effect versus Electrostatic Doping

“…The predicted electric field required to provide the same shift as in the experiment is less in the calculation, which indicates a strong screening 44 in the bilayer WS 2 , particularly in the presence of optical excitation. At higher |ξ|, the experimental Stark shift deviates from linearity as the rate of shift reduces, pointing to strong excitonic effects 45 in the QCSE. The exciton binding energy (ζ b ) reduces at higher electric field, which results in a blue shift in the X 0 position, partially compensating the QCSE induced red shift.…”