Valley Polarization Dynamics of Inter- and Intra-valley Trions in Monolayer WSe2

Singh, Akshay; Tran, Kha; Seifert, Joe; Wang, Yiping; Hao, Kai; Li, Xiaoqin; Pleskot, Dennis; Gabor, Nathaniel; Helmrich, Sophia; Kolarczik, Mirco; Owschimikow, Nina; Woggon, U.

doi:10.1364/cleo_qels.2017.ff2f.5

Cited by 19 publications

(26 citation statements)

References 4 publications

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“…Recent work has demonstrated subpicosecond trion formation, 81 coherent and incoherent exciton−trion coupling, 82−84 and increased trion valley polarization lifetimes. 22,85 While the broad spectral features in our work preclude the observation of a possible distinct trion resonance, 86 intervalley coupling signatures are observed largely across entire spectral features, whereas trion-mediated coupling would appear predominantly at either excitation or detection energies that are red-shifted from the main exciton peak, such as the A−A ( ′ ) feature. For these reasons, the intervalley coupling signatures observed in our work likely do not originate from exciton−trion or trion− trion valley coupling.…”

Section: Resultsmentioning

confidence: 71%

Sub-10 fs Intervalley Exciton Coupling in Monolayer MoS₂ Revealed by Helicity-Resolved Two-Dimensional Electronic Spectroscopy

et al. 2021

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The valley pseudospin at the K and K′ high-symmetry points in monolayer transition metal dichalcogenides (TMDs) has potential as an optically addressable degree of freedom in next-generation optoelectronics. However, intervalley scattering and relaxation of charge carriers leads to valley depolarization and limits practical applications. In addition, enhanced Coulomb interactions lead to pronounced excitonic effects that dominate the optical response and initial valley depolarization dynamics but complicate the interpretation of ultrafast spectroscopic experiments at short time delays. Employing broadband helicity-resolved two-dimensional electronic spectroscopy (2DES), we observe ultrafast (∼10 fs) intervalley coupling between all A and B valley exciton states that results in a complete breakdown of the valley index in large-area monolayer MoS 2 films. These couplings and subsequent dynamics exhibit minimal excitation fluence or temperature dependence and are robust toward changes in sample grain size and inherent strain. Our observations strongly suggest that this direct intervalley coupling on the time scale of optical excitation is an inherent property of large-area MoS 2 distinct from dynamic carrier or exciton scattering, phonon-driven processes, and multiexciton effects. This ultrafast intervalley coupling poses a fundamental challenge for exciton-based valleytronics in monolayer TMDs and must be overcome to fully realize large-area valleytronic devices.

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Section: Resultsmentioning

confidence: 71%

Sub-10 fs Intervalley Exciton Coupling in Monolayer MoS₂ Revealed by Helicity-Resolved Two-Dimensional Electronic Spectroscopy

et al. 2021

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“…The relatively strong emission intensity of D 0 is a result of the large population of dark excitons (ground state). The dynamics between different exciton species determines their lifetimes ranging from a few ps in the case of bright excitons up to a ns when dealing with dark excitons in WSe 2 monolayer [1,22]. The resonance I 0 emerges slightly below 1.68 eV and is best seen at low power excitation.…”

Section: The Emission Spectrum In (Nearly) Charge-neutral Monolayer Wse2mentioning

confidence: 99%

Intervalley electron-hole exchange interaction and impurity-assisted recombination of indirect excitons in WS$_2$ and WSe$_2$ monolayers

Li,

Robert,

Van Tuan

et al. 2022

Preprint

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The variety of excitonic states in tungsten-based dichalcogenide monolayers stems from unique interplay between the spin and valley degrees of freedom. One of the exciton species is the indirect exciton (momentum or valley dark), which is responsible to a series of resonances when the monolayer is charge neutral. We investigate the short-range electron-hole exchange interaction of the indirect exciton, as well as its recombination mechanism mediated by impurities. The analysis provides thorough understanding of the energy and polarization of the zero-phonon indirect exciton resonance in the emission spectrum.

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“…Generally, the TMD monolayer has two degenerate but inequivalent valleys (K and K¢) which prefer to couple to RCP or LCP, respectively. Under incident circularly polarized light excitation, valley-polarized PL emission has been reported for TMDs [46][47][48]. The in the presence of chiral plasmonic metasurface with left-handedness, there will be two different results.…”

Section: Chiral Plasmonics Modulated Quantum Emissionmentioning

confidence: 99%

Chiral plasmonics and enhanced chiral light-matter interactions

Wen

Gérard

et al. 2019

Sci. China Phys. Mech. Astron.

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Chirality, which describes the broken mirror symmetry in geometric structures, exists macroscopically in our daily life as well as microscopically down to molecular levels. Correspondingly, chiral molecules interact differently with circularly polarized light exhibiting opposite handedness (left-handed and right-handed). However, the interaction between chiral molecules and chiral light is very weak. In contrast, artificial chiral plasmonic structures can generate "super-chiral" plasmonic near-field, leading to enhanced chiral light-matter (or chiroptical) interactions. The "super-chiral" near-field presents different amplitude and phase under opposite handedness incidence, which can be utilized to engineer linear and nonlinear chiroptical interactions. Specifically, in the interaction between quantum emitters and chiral plasmonic structures, the chiral hot spots can favour the emission with a specific handedness. This article reviews the state-of-the-art research on the design, fabrication and chiroptical response of different chiral plasmonic nanostructures or metasurfaces. This review also discusses enhanced chiral light-matter interactions that are essential for applications like chirality sensing, chiral selective light emitting and harvesting. In the final part, the review ends with a perspective on future directions of chiral plasmonics.

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Valley Polarization Dynamics of Inter- and Intra-valley Trions in Monolayer WSe2

Cited by 19 publications

References 4 publications

Sub-10 fs Intervalley Exciton Coupling in Monolayer MoS₂ Revealed by Helicity-Resolved Two-Dimensional Electronic Spectroscopy

Sub-10 fs Intervalley Exciton Coupling in Monolayer MoS₂ Revealed by Helicity-Resolved Two-Dimensional Electronic Spectroscopy

Intervalley electron-hole exchange interaction and impurity-assisted recombination of indirect excitons in WS$_2$ and WSe$_2$ monolayers

Chiral plasmonics and enhanced chiral light-matter interactions

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Valley Polarization Dynamics of Inter- and Intra-valley Trions in Monolayer WSe2

Cited by 19 publications

References 4 publications

Sub-10 fs Intervalley Exciton Coupling in Monolayer MoS2 Revealed by Helicity-Resolved Two-Dimensional Electronic Spectroscopy

Sub-10 fs Intervalley Exciton Coupling in Monolayer MoS2 Revealed by Helicity-Resolved Two-Dimensional Electronic Spectroscopy

Intervalley electron-hole exchange interaction and impurity-assisted recombination of indirect excitons in WS$_2$ and WSe$_2$ monolayers

Chiral plasmonics and enhanced chiral light-matter interactions

Contact Info

Product

Resources

About

Sub-10 fs Intervalley Exciton Coupling in Monolayer MoS₂ Revealed by Helicity-Resolved Two-Dimensional Electronic Spectroscopy

Sub-10 fs Intervalley Exciton Coupling in Monolayer MoS₂ Revealed by Helicity-Resolved Two-Dimensional Electronic Spectroscopy