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.

7 pages, 3 figures, supplement

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Cited by in corpus (31)

• Controlling interlayer excitons in MoS2 layers grown by chemical vapor deposition
• Theory of exciton-electron scattering in atomically thin semiconductors
• Guide to optical spectroscopy of layered semiconductors
• Intrinsic Lifetime of Higher Excitonic States in Tungsten Diselenide Monolayers
• Cathodoluminescence excitation spectroscopy: nanoscale imaging of excitation pathways
• Asymmetric magnetic proximity interactions in MoSe${}_2$/CrBr${}_3$ van der Waals heterostructures
• Boosting quantum yields in 2D semiconductors via proximal metal plates
• Second harmonic generation control in twisted bilayers of transition metal dichalcogenides
• 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
• Exposing the trion's fine structure by controlling the carrier concentration in hBN-encapsulated MoS${}_2$
• Band nesting and exciton spectrum in monolayer MoS${}_2$
• Phonon-assisted exciton and trion conversion efficiency in transition metal Dichalcogenides
• Control of the exciton valley dynamics in van der Waals heterostructures
• Magnetoexcitons in transition-metal dichalcogenides monolayers, bilayers, and van der Waals heterostructures
• Direct Observation of Intravalley Phonon Scattering of 2s Excitons in MoSe${}_2$ and WSe${}_2$ Monolayers
• Excited-State Trions in Two Dimensional Materials
• Room Temperature Micro-Photoluminescence Studies of Colloidal WS2 Nanosheets
• Calculation of the nonlinear response functions of intra-exciton transitions in two-dimensional transition metal dichalcogenides
• Effects of parallel electric and magnetic fields on Rydberg excitons in buckled two-dimensional materials
• Theory of the Coherent Response of Magneto-Excitons and Magneto-Biexcitons in Monolayer Transition Metal Dichalcogenides
• The Importance of Pure Dephasing in the Optical Response of Excitons in High-quality van der Waals Heterostructures
• Tuning nanowire lasers via hybridization with two-dimensional materials
• Third-order polarizability of interlayer excitons in hetero-bilayers
• Magnetic Correlation Spectroscopy in CrSBr
• Nonexponential photoluminescence dynamics in an inhomogeneous ensemble of excitons in WSe${}_2$ monolayers
• Charge-separated electron-hole liquid in transition metal dichalcogenide heterostructures
• Energy shifts and broadening of excitonic resonances in electrostatically-doped semiconductors
• High-temperature tunable superfluidity of polaritons in Xene monolayers in an optical microcavity
• Photoluminescence efficiency of MBE-grown MoSe${}_2$ monolayers featuring sharp excitonic lines and diverse grain structures
• The Transmission Line Model for 2D Materials and van der Waals Heterostructures