Optical spectroscopy of excited exciton states in MoS2 monolayers in van der Waals heterostructures

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 to extrapolate an exciton binding energy of about 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.

arXiv comment7 pages, 3 figures, supplement

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• Controlling interlayer excitons in MoS2 layers grown by chemical vapor deposition
• Accessing high optical quality of MoS2 monolayers grown by chemical vapor deposition
• Theory of exciton-electron scattering in atomically thin semiconductors
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• Energy spectrum of two-dimensional excitons in a non-uniform dielectric medium
• Shubnikov-de Haas oscillations in optical conductivity of monolayer MoSe${}_2$
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• Asymmetric magnetic proximity interactions in MoSe${}_2$/CrBr${}_3$ van der Waals heterostructures
• Excitons, trions, and biexcitons in transition metal dichalcogenides: magnetic field dependence
• Dependence of the hBN Layer Thickness on the Band Structure and Exciton Properties of Encapsulated WSe2 Monolayers
• Boosting quantum yields in 2D semiconductors via proximal metal plates
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• Spinorial formulation of the GW-BSE equations and spin properties of excitons in 2D Transition Metal Dichalcogenides
• Autoionization and dressing of excited excitons by free carriers in monolayer WSe2
• Radiative lifetime of localized excitons in transition metal dichalcogenides
• On the Optical Properties of Excitons in Buckled 2D Materials in an External Electric Field
• Exposing the trion's fine structure by controlling the carrier concentration in hBN-encapsulated MoS${}_2$
• Optical nonlinearities of excitons in monolayer MoS2
• Band nesting and exciton spectrum in monolayer MoS${}_2$
• Optical Properties of Anisotropic Excitons in Phosphorene
• Phonon-assisted exciton and trion conversion efficiency in transition metal Dichalcogenides
• Control of the exciton valley dynamics in van der Waals heterostructures
• Direct Observation of Intravalley Phonon Scattering of 2s Excitons in MoSe${}_2$ and WSe${}_2$ Monolayers
• Magnetoexcitons in transition-metal dichalcogenides monolayers, bilayers, and van der Waals heterostructures
• Excited-State Trions in Two Dimensional Materials
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• Room Temperature Micro-Photoluminescence Studies of Colloidal WS2 Nanosheets
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• Theory of the Coherent Response of Magneto-Excitons and Magneto-Biexcitons in Monolayer Transition Metal Dichalcogenides
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• Third-order polarizability of interlayer excitons in hetero-bilayers
• Magnetic Correlation Spectroscopy in CrSBr
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• The Transmission Line Model for 2D Materials and van der Waals Heterostructures
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