Coulomb interaction in monolayer transition-metal dichalcogenides

Tuan, Dinh Van; Yang, Min-Fong; Dery, Hanan

doi:10.1103/physrevb.98.125308

Cited by 129 publications

(115 citation statements)

References 68 publications

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“…This function can be described through the Rytova-Keldysh potential of a thin semiconductor, 87-91 first-principles calculations, 70,71 or a model that considers a ML-TMDs as a system made of three atomic sheets. 57 All of these non-local dielectric function models converge to the value given by the average effective dielectric constants of the materials below and above the ML when q → 0. Therefore, they yield qualitatively similar results for the Coulomb-hole energy.…”

Section: Results and Conclusionmentioning

confidence: 83%

“…The amount by which we increase the effective mass is found from matching the trion (charged exciton) binding energy to the empirical values. 57 Very good agreement is achieved when the polaron effect amounts to an increase of ∼17% in the effective mass of charged particles in ML-WSe 2 and ∼25% in ML-MoSe 2 . The larger mass increase in ML-MoSe 2 stems from the larger Fröhlich interaction in this material.…”

Section: B Parametersmentioning

confidence: 79%

“…The latter is found from the in-plane and out-of-plane components according to, = √ ∞ , and it becomes ∼3.8 in the high-frequency regime and ∼4.9 in the static limit. 57 The thickness of the h-BN layer is t ∼ 20 nm, and V is the combined top and back gate voltage. We then get that 1 V is equivalent to a doping density of ∼ 10 12 cm −2 .…”

Section: Methodsmentioning

confidence: 99%

“…73 Binding energies in charge neutrality conditions: We have employed the stochastic variational method calculations and parameters from Ref. [57], and got the following binding energies of direct and indirect excitons in chargeneutrality conditions. |E d | and |E i | are 178 and 195 meV, respectively, in h-BN/WSe 2 /h-BN.…”

Section: B Parametersmentioning

confidence: 99%

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Probing many-body interactions in monolayer transition-metal dichalcogenides

et al. 2019

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Many-body interactions in monolayer transition-metal dichalcogenides are strongly affected by their unique band structure. We study these interactions by measuring the energy shift of neutral excitons (bound electron-hole pairs) in gated WSe2 and MoSe2. Surprisingly, while the blueshift of the neutral exciton, X 0 , in electron-doped samples can be more than 10 meV, the blueshift in hole-doped samples is nearly absent. Taking into account dynamical screening and local-field effects, we present a transparent and analytical model that elucidates the crucial role played by intervalley plasmons in electron-doped conditions. The energy shift of X 0 as a function of charge density is computed showing agreement with experiment, where the renormalization of X 0 by intervalley plasmons yields a stronger blueshift in MoSe2 than in WSe2 due to differences in their band ordering. * hanan.dery@rochester.edu 1

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Section: Results and Conclusionmentioning

confidence: 83%

Section: B Parametersmentioning

confidence: 79%

Section: Methodsmentioning

confidence: 99%

Section: B Parametersmentioning

confidence: 99%

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Probing many-body interactions in monolayer transition-metal dichalcogenides

et al. 2019

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“…The chosen values of all parameters are explained in Ref. [89]. Next, we discuss how the bare Coulomb interaction changes by the presence of other charge carriers.…”

Section: Introductionmentioning

confidence: 99%

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

Scharf

Tuan

Žutić

et al. 2019

J. Phys.: Condens. Matter

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Monolayer transition-metal dichalcogenides (ML-TMDs) offer exciting opportunities to test the manifestations of many-body interactions through changes in the charge density. The two-dimensional character and reduced screening in ML-TMDs lead to the formation of neutral and charged excitons with binding energies orders of magnitude larger than those in conventional bulk semiconductors. Tuning the charge density by a gate voltage leads to profound changes in the optical spectra of excitons in ML-TMDs. On the one hand, the increased screening at large charge densities should result in a blueshift of the exciton spectral lines due to reduction in the binding energy. On the other hand, exchange and correlation effects that shrink the band-gap energy at elevated charge densities (band-gap renormalization) should result in a redshift of the exciton spectral lines. While these competing effects can be captured through various approximations that model long-wavelength charge excitations in the Bethe-Salpeter Equation, we show that a novel 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 K and −K valleys. The shortwave plasmons have a finite energy-gap because of the removal of spin-degeneracy in both the valence-arXiv:1801.06217v2 [cond-mat.mtrl-sci] 2. Properties of monolayer transition-metal dichalcogenides ML-TMDs are direct band-gap semiconductors with the conduction band and valence band edges at the K and K = −K points [19]. These time-reversed points define two separate low-energy pockets/valleys in the Brillouin zone. Due to the lack of space inversion symmetry and strong spin-orbit coupling arising from the d orbitals of the transition-metal atoms, the spin degeneracy in these valleys is lifted [24], as shown in Figs. 1(a,c). Whereas the spin splitting ∆ c in the conduction band is typically at most a few 10s of meV, the spin splitting in the valence band can be several 100s meV [24,54,55,56,57]. There are two important aspects to this band structure: First, timereversal symmetry results in a coupling between the spin and valley degrees of freedom, such that the spin ordering in opposite valleys is reversed as illustrated in Figs. 1(a,c). Second, the spin ordering of the conduction band in Mo-based compounds is opposite to the one in W-based compounds, as can be seen by comparing Figs. 1(a) and (c) [24,57,58]. This difference will be shown below to have profound consequences on their optical properties. Due to the large spin-splitting energy of the valence band, one can distinguish between two different series of neutral excitons in absorption experiments: One series involving the top valleys in the valence band, usually denoted as A excitons, and one involving it...

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Superradiant Emission from Coherent Excitons in van Der Waals Heterostructures

Haider

Sampathkumar

Verhagen

et al. 2021

Adv Funct Materials

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Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition-metal dichalcogenides (TMDs) and few-layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic-dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many-body correlations and other state-of-the-art technologies. This timely demonstration paves the way for further exploration of ultralow-threshold quantumemitting devices with unmatched design freedom and spectral tunability.

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Coulomb interaction in monolayer transition-metal dichalcogenides

Cited by 129 publications

References 68 publications

Probing many-body interactions in monolayer transition-metal dichalcogenides

Probing many-body interactions in monolayer transition-metal dichalcogenides

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

Superradiant Emission from Coherent Excitons in van Der Waals Heterostructures

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