Optical spectroscopy of excited exciton states in MoS 2 monolayers in van der Waals heterostructures - INSA Toulouse - Institut National des Sciences Appliquées de Toulouse Access content directly
Journal Articles Physical Review Materials Year : 2018

Optical spectroscopy of excited exciton states in MoS 2 monolayers in van der Waals heterostructures

K. Watanabe
Thierry Amand
M. Glazov

Abstract

The optical properties of MoS2 monolayers are dominated by excitons, but for spectrally broad optical transitions in monolayers exfoliated directly onto SiO2 substrates detailed information on excited exciton states is inaccessible. Encapsulation in hexagonal boron nitride (hBN) allows approaching the homogenous exciton linewidth, but interferences in the van der Waals heterostructures make direct comparison between transitions in optical spectra with different oscillator strength more challenging. Here we reveal in reflectivity and in photoluminescence excitation spectroscopy the presence of excited states of the A exciton in MoS2 monolayers encapsulated in hBN layers of calibrated thickness, allowing us to extrapolate an exciton binding energy of ≈220 meV. We theoretically reproduce the energy separations and oscillator strengths measured in reflectivity by combining the exciton resonances calculated for a screened two-dimensional Coulomb potential with transfer matrix calculations of the reflectivity for the van der Waals structure. Our analysis shows a very different evolution of the exciton oscillator strength with principal quantum number for the screened Coulomb potential as compared to the ideal two-dimensional hydrogen model.
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Dates and versions

hal-02057607 , version 1 (18-04-2019)

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Cédric Robert, M. Semina, Fabian Cadiz, Marco Manca, Emmanuel Courtade, et al.. Optical spectroscopy of excited exciton states in MoS 2 monolayers in van der Waals heterostructures. Physical Review Materials, 2018, 2 (1), ⟨10.1103/PhysRevMaterials.2.011001⟩. ⟨hal-02057607⟩
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