3 years ago

Observation of Exciton Redshift–Blueshift Crossover in Monolayer WS2

Observation of Exciton Redshift–Blueshift Crossover in Monolayer WS2
N. Gedik, E. J. Sie, C. Gies, F. Jahnke, P. Jarillo-Herrero, J. Kong, G. Schönhoff, M. Rösner, C. H. Lui, Y.-H. Lee, T. O. Wehling, A. Steinhoff, Q. Ma
We report a rare atom-like interaction between excitons in monolayer WS2, measured using ultrafast absorption spectroscopy. At increasing excitation density, the exciton resonance energy exhibits a pronounced redshift followed by an anomalous blueshift. Using both material-realistic computation and phenomenological modeling, we attribute this observation to plasma effects and an attraction–repulsion crossover of the exciton–exciton interaction that mimics the Lennard-Jones potential between atoms. Our experiment demonstrates a strong analogy between excitons and atoms with respect to interparticle interaction, which holds promise to pursue the predicted liquid and crystalline phases of excitons in two-dimensional materials.

Publisher URL: http://dx.doi.org/10.1021/acs.nanolett.7b01034

DOI: 10.1021/acs.nanolett.7b01034

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