Observation of exciton redshift-blueshift crossover in monolayer WS2  (Conference Presentation)

Christopher Gies; Edbert J. Sie; Alexander Steinhoff; C. H. Lui; Q. Ma; Malte Rösner; Gunnar Schönhoff; Frank Jahnke; Tim O. Wehling; Y.-H. Lee; J. Kong; P. Jarillo-Herrero; Nuh Gedik

doi:10.1117/12.2287771

14 March 2018 Observation of exciton redshift-blueshift crossover in monolayer WS₂ (Conference Presentation)

Christopher Gies, Edbert J. Sie, Alexander Steinhoff, C. H. Lui, Q. Ma, Malte Rösner, Gunnar Schönhoff, Frank Jahnke, Tim O. Wehling, Y.-H. Lee, J. Kong, P. Jarillo-Herrero, Nuh Gedik

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Proceedings Volume 10534, 2D Photonic Materials and Devices; 1053408 (2018) https://doi.org/10.1117/12.2287771
Event: SPIE OPTO, 2018, San Francisco, California, United States

Abstract

Atomically thin transition-metal dichalcogenide (TMD) semiconductors possess strong Coulomb interactions due to reduced dielectric screening, leading to the formation of excitons with exceptionally large binding energies. The enhanced stability of excitons in these materials provides a unique platform to investigate excitonic interactions at room temperature and to examine the role of plasma effects and excitonic interactions over a broad range of excitation densities. We report an excitation-density dependent crossover between two regimes: Using ultrafast absorption spectroscopy, we observe a pronounced red shift of the exciton resonance followed by an anomalous blue shift with increasing excitation density. Using both material-realistic computation and phenomenological modeling, we attribute this observation to long-range Coulomb interaction in the presence of plasma screening in an attraction-repulsion crossover with the short-ranged exciton-exciton interaction that mimics the Lennard-Jones potential between atoms, suggesting a strong analogy between excitons and atoms in respect of inter-particle interaction. Our findings underline the important role of many-particle renormalizations and screening due to excited carriers in the device-relevant regime of optically or electrically excited TMDs.

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Christopher Gies, Edbert J. Sie, Alexander Steinhoff, C. H. Lui, Q. Ma, Malte Rösner, Gunnar Schönhoff, Frank Jahnke, Tim O. Wehling, Y.-H. Lee, J. Kong, P. Jarillo-Herrero, and Nuh Gedik "Observation of exciton redshift-blueshift crossover in monolayer WS₂ (Conference Presentation)", Proc. SPIE 10534, 2D Photonic Materials and Devices, 1053408 (14 March 2018); https://doi.org/10.1117/12.2287771

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KEYWORDS

Excitons

Plasma

Absorption spectroscopy

Chemical species

Dielectrics

Doping

Modeling

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