Anomalous Non-Hydrogenic Exciton Series in 2D Materials on High-$\kappa$ Dielectric Substrates

Abstract

Engineering of the dielectric environment represents a powerful strategy to control the electronic and optical properties of two-dimensional (2D) materials without compromising their structural integrity. Here we show that the recent development of high-$\kappa$ 2D materials present new opportunities for dielectric engineering. By solving a 2D Mott-Wannier exciton model for WSe${}_2$ on different substrates using a screened electron-hole interaction obtained from first principles, we demonstrate that the exciton Rydberg series changes qualitatively when the dielectric screening within the 2D semiconductor becomes dominated by the substrate. In this regime, the distance dependence of the screening is reversed and the effective screening increases with exciton radius, which is opposite to the conventional 2D screening regime. Consequently, higher excitonic states become underbound rather than overbound as compared to the Hydrogenic Rydberg series. Finally, we derive a general analytical expression for the exciton binding energy of the entire 2D Rydberg series

References in corpus (5)

• Observation of giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor
• Observation of Moiré Excitons in WSe2/WS2 Heterostructure Superlattices
• Engineering of Neutral Excitons and Exciton Complexes in Transition Metal Dichalcogenide Monolayers through External Dielectric Screening
• Magneto-photoluminescence of exciton Rydberg states in monolayer WSe${}_2$
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• Roadmap for Photonics with 2D Materials
• Breakdown of the static dielectric screening approximation of Coulomb interactions in atomically thin semiconductors
• Delocalization of dark and bright excitons in flat-band materials and the optical properties of V${}_2$O${}_5$
• Exciton spectrum in atomically thin monolayers: The role of hBN encapsulation
• Substrate Effect on Excitonic Shift and Radiative Lifetime of Two-Dimensional Materials