Role of dark exciton states in the relaxation dynamics of bright 1s excitons in monolayer WSe2

Kusaba, Satoshi; Watanabe, Kenji; Taniguchi, Takashi; Yanagi, Kazuhiro; Tanaka, Kōichiro

doi:10.1063/5.0064795

Cited by 5 publications

(1 citation statement)

References 49 publications

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“…Therefore, when the contributions from k and −k points are summed together, they cancel each other and make the exciton dark, as predicted by the model. Such a robust dark exciton can play a key role for many disexcitation processes [66][67][68][69] , such as phonon-assisted luminescence and light emission.…”

Section: /14mentioning

confidence: 99%

Delocalization of dark and bright excitons in flat-band materials and the optical properties of V$_2$O$_5$

Gorelov,

Reining,

Feneberg

et al. 2022

Preprint

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The simplest picture of excitons in materials with atomic-like localization of electrons is that of Frenkel excitons, where electrons and holes stay close together, which is associated with a large binding energy. Here, using the example of the layered oxide V 2 O 5 , we show how localized charge-transfer excitations combine to form excitons that also have a huge binding energy but, at the same time, a large electron-hole distance, and we explain this seemingly contradictory finding. The anisotropy of the exciton delocalization is determined by the local anisotropy of the structure, whereas the exciton extends orthogonally to the chains formed by the crystal structure. Moreover we show that the bright exciton goes together with a dark exciton of even larger binding energy and more pronounced anisotropy. These findings are obtained by combining first principles many-body perturbation theory calculations, ellipsometry experiments, and tight binding modelling, leading to very good agreement and a consistent picture. Our explanation is general and can be extended to other materials.

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Section: /14mentioning

confidence: 99%

Delocalization of dark and bright excitons in flat-band materials and the optical properties of V$_2$O$_5$

Gorelov,

Reining,

Feneberg

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

Delocalization of dark and bright excitons in flat-band materials and the optical properties of V2O5

et al. 2022

View full text Add to dashboard Cite

The simplest picture of excitons in materials with atomic-like localization of electrons is that of Frenkel excitons, where electrons and holes stay close together, which is associated with a large binding energy. Here, using the example of the layered oxide V2O5, we show how localized charge-transfer excitations combine to form excitons that also have a huge binding energy but, at the same time, a large electron-hole distance, and we explain this seemingly contradictory finding. The anisotropy of the exciton delocalization is determined by the local anisotropy of the structure, whereas the exciton extends orthogonally to the chains formed by the crystal structure. Moreover, we show that the bright exciton goes together with a dark exciton of even larger binding energy and more pronounced anisotropy. These findings are obtained by combining first principles many-body perturbation theory calculations, ellipsometry experiments, and tight binding modelling, leading to very good agreement and a consistent picture. Our explanation is general and can be extended to other materials.

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Observation of enhanced WSe2 exciton–exciton annihilation in WSe2/Gr/hBN heterostructure

Wang,

Chen,

Sun

et al. 2024

Applied Physics Letters

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Due to strong quantum confinement effects and novel physical properties, two-dimensional transition metal dichalcogenides (TMDCs) as well as their heterostructures provide an attractive platform for studying excitonic effects and many-body interactions. However, manipulation on the excitonic effect in TMDCs remains challenge owing to the complex interplay of various factors. In this Letter, we report large exciton peak redshift and enhanced exciton–exciton annihilation in WSe2/Gr/hBN heterostructures investigated with static and transient optical spectroscopy. The pronounced redshift of exciton energy in the triple layer heterostructure arises from the charge transfer effect between graphene and WSe2, which leads to the reduction of the WSe2 exciton binding energy significantly due to the Coulomb screening effect. As a result, the reduced exciton binding energy increases the exciton delocalization in the WSe2 layer, leading to an increased probability of exciton–exciton collisions, which results in fast exciton annihilation rate. This study demonstrates the impact of graphene layer on exciton energy as well as the relaxation dynamics in WSe2/Gr/hBN heterostructures, which provides insights into the understanding of quasiparticle physics and many-body interactions in 2D materials.

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Role of dark exciton states in the relaxation dynamics of bright 1s excitons in monolayer WSe2

Cited by 5 publications

References 49 publications

Delocalization of dark and bright excitons in flat-band materials and the optical properties of V$_2$O$_5$

Delocalization of dark and bright excitons in flat-band materials and the optical properties of V$_2$O$_5$

Delocalization of dark and bright excitons in flat-band materials and the optical properties of V2O5

Observation of enhanced WSe2 exciton–exciton annihilation in WSe2/Gr/hBN heterostructure

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