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Coherent Interaction of 2s and 1s Exciton States in Transition-Metal Dichalcogenide Monolayers
Max Wegerhoff1, Moritz Scharfstädt1, Stefan Linden1
1University of Bonn, Physikalisches Institut, 53115 Bonn, Germany.
Abstract:
We use femtosecond pump-probe spectroscopy to study the coherent interaction of excited exciton states in WSe_{2} and MoSe_{2} monolayers via the optical Stark effect. For cocircularly polarized pump and probe, we measure a blueshift that points to a repulsive interaction between the 2s and 1s exciton states. The determined 2s-1s interaction strength is on par with that of the 1s-1s in agreement with the semiconductor Bloch equations. Furthermore, we demonstrate the existence of a 2s-1s biexciton bound state in the cross-circular configuration in both materials and determine their binding energy.
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