Dynamical screening in monolayer transition-metal dichalcogenides and its manifestations in the exciton spectrum

Abstract

Monolayer transition-metal dichalcogenides (ML-TMDs) offer exciting opportunities to test the manifestations of many-body interactions through changes in the charge density. Tuning the charge density by a gate voltage leads to profound changes in the optical spectra of excitons in ML-TMDs. We review the band-gap renormalization and dynamical screening as a function of charge density, and then incorporate these effects through various approximations that model long-wavelength charge excitations in the Bethe-Salpeter Equation (BSE). We then show that coupling between excitons and shortwave charge excitations is essential to resolve several experimental puzzles. Unlike ubiquitous and well-studied plasmons, driven by collective oscillations of the background charge density in the long-wavelength limit, we discuss the emergence of shortwave plasmons that originate from the short-range Coulomb interaction through which electrons transition between the $\mathbf{K}$ and $-\mathbf{K}$ valleys. We study the coupling between the shortwave plasmons and the neutral exciton through the self-energy of the latter. We then elucidate how this coupling as well as the spin ordering in the conduction band give rise to an experimentally observed optical sideband in electron-doped W-based MLs, conspicuously absent in electron-doped Mo-based MLs or any hole-doped ML-TMDs. While the focus of this review is on the optical manifestations of many-body effects in ML-TMDs, a systematic description of the dynamical screening and its various approximations allow one to revisit other phenomena, such as nonequilibrium transport or superconducting pairing, where the use of the BSE or the emergence of shortwave plasmons can play an important role.

This revised version is far more extensive. Any feedback is welcome

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• Optospintronics in graphene via proximity coupling
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• Theory of exciton dynamics in time-resolved ARPES: intra- and intervalley scattering in two-dimensional semiconductors
• Measurement of Conduction and Valence Bands g-factors in a Transition Metal Dichalcogenide Monolayer
• Efficient phonon cascades in hot photoluminescence of WSe${}_2$ monolayers
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• Relaxation and darkening of excitonic complexes in electrostatically-doped monolayer semiconductors: Roles of exciton-electron and trion-electron interactions
• Localized Excitons in NbSe${}_2$-MoSe${}_2$ Heterostructures
• Giant proximity exchange and valley splitting in transition metal dichalcogenide/$h\mathrm{BN}$/(Co, Ni) heterostructures
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• Trion induced photoluminescence of a doped MoS2 monolayer
• Optically Probing Tunable Band Topology in Atomic Monolayers
• Few-body systems in condensed matter physics
• Band nesting and exciton spectrum in monolayer MoS${}_2$
• Many-body exciton and inter-valley correlations in heavily electron-doped WSe${}_2$ monolayers
• Breakdown of the static dielectric screening approximation of Coulomb interactions in atomically thin semiconductors
• Three-particle states and brightening of intervalley excitons in a doped MoS${}_2$ monolayer
• Microscopic model of the doping dependence of line widths in monolayer transition metal dichalcogenides
• Composite excitonic states in doped semiconductors
• Unconventional Spintronics from Chiral Perovskites
• Charge Density Wave Activated Excitons in TiSe${}_2$-MoSe${}_2$ Heterostructures
• Effect of dynamical screening in the Bethe-Salpeter framework: Excitons in crystalline naphthalene
• Emergence of 6-particle "hexciton'' states in WS${}_2$ and MoSe${}_2$ monolayers
• Intervalley electron-hole exchange interaction and impurity-assisted recombination of indirect excitons in WS${}_2$ and WSe${}_2$ monolayers
• Effects of dynamical dielectric screening on the excitonic spectrum of monolayer semiconductors
• Algorithm for Reproducible Analysis of Semiconducting 2D Nanomaterials Based on UV/VIS Spectroscopy
• Unidirectional valley-contrasting photo-current in strained transition metal dichalcogenide monolayers
• Flat-band-induced many-body interactions and exciton complexes in a layered semiconductor
• Excitonic Tonks-Girardeau and charge-density wave phases in monolayer semiconductors
• Symmetry Classification for Alternating Excitons in Two-Dimensional Altermagnets
• Excitons and trions in CrSBr bilayers
• Excitons in Atomically Thin TMD in Electric and Magnetic Fields
• Doping-induced non-Markovian interference causes excitonic linewidth broadening in monolayer WSe${}_2$
• Component exchange theory of trions
• Tunable resonant s-p mixing of excitons in van der Waals heterostructures
• Exchange-enhanced spin-orbit splitting and its density dependence for electrons in monolayer transition metal dichalcogenides
• Energy shifts and broadening of excitonic resonances in electrostatically-doped semiconductors