| 1. |
- de Amorim Ferreira, Beatriz, 1996, et al.
(författare)
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Revealing Dark Exciton Signatures in Polariton Spectra of 2D Materials
- 2024
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Ingår i: ACS Photonics. - 2330-4022. ; 11:6, s. 2215-2220
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Tidskriftsartikel (refereegranskat)abstract
- Dark excitons in transition metal dichalcogenides (TMDs) have been so far neglected in the context of polariton physics due to their lack of oscillator strength. However, in tungsten-based TMDs, dark excitons are known to be the energetically lowest states and could thus provide important scattering partners for polaritons. In this joint theoretical-experimental work, we investigate the impact of the full exciton energy landscape on polariton absorption and reflectance. By changing the cavity detuning, we vary the polariton energy relative to the unaffected dark excitons in such a way that we open or close specific phonon-driven scattering channels. We demonstrate both in theory and experiment that this controlled switching of scattering channels manifests in characteristic sharp changes in the optical spectra of polaritons. These spectral features can be exploited to extract the position of dark excitons. Our work suggests new possibilities for exploiting polaritons for fingerprinting nanomaterials via their unique exciton landscape.
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| 2. |
- Han, Bo, et al.
(författare)
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Angle- and polarization-resolved luminescence from suspended and hexagonal boron nitride encapsulated MoSe2 monolayers
- 2022
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Ingår i: Optica. - 2334-2536. ; 9:10, s. 1190-1196
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Tidskriftsartikel (refereegranskat)abstract
- The polarized photoluminescence from atomically thin transition metal dichalcogenides is a frequently applied tool to scrutinize optical selection rules and valley physics, yet it is known to sensibly depend on a variety of internal and external material and sample properties. In this work, we apply combined angle- and polarization-resolved spectroscopy to explore the interplay of excitonic physics and phenomena arising from the commonly utilized encapsulation procedure on the optical properties of atomically thinMoSe2.We probe monolayers prepared in both suspended and encapsulated manners.We show that the hBN encapsulation significantly enhances the linear polarization of exciton photoluminescence emission at large emission angles. This degree of linear polarization of excitons can increase up to ∼17% in the hBN encapsulated samples. As we confirm by finite-difference time-domain simulations, it can be directly connected to the optical anisotropy of the hBN layers. In comparison, the linear polarization at finite exciton momenta is significantly reduced in a suspendedMoSe2 monolayer, and becomes notable only in cryogenic conditions. This phenomenon strongly suggests that the effect is rooted in the k-dependent anisotropic exchange coupling inherent in2Dexcitons.Our results have strong implications on further studies on valley contrasting selection rules and valley coherence phenomena using standard suspended and encapsulated samples.
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| 3. |
- Palekar, Chirag, et al.
(författare)
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Anomalous redshift in interlayer exciton emission with increasing twist angle in WSe 2 /MoSe 2 heterostructures
- 2024
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Ingår i: 2D Materials. - 2053-1583. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- Van der Waals heterostructures utilizing semiconducting transition metal dichalcogenide (TMDC) monolayers have surfaced as compelling candidates due to their intriguing optical characteristics, which can be effectively controlled by the manipulation of the stacking twist angle. This study investigates the intricate correlation between twist angle, band offset, and interlayer exciton emission within twisted WSe2/MoSe2 heterostructures. Our findings suggest a crucial influence of monolayer stacking order on the band offset and the dipole orientation in twisted heterostructures that leads to either blueshift or redshift in emission energy. Herein, we fabricate heterobilayers with twist angles varying from 1 ∘ to 56 ∘ and observe an anomalous redshift energy of 100 meV in the interlayer exciton emission. Additionally, photoluminescence excitation spectroscopy measurements highlight the systematic twist angle dependence of intralayer exciton resonances, indicating significant angle dependent effects on individual monolayer bandgaps and on the interlayer coupling strength. Our fundamental study of exciton resonances provides comprehensive insights into the nuanced interplay between twist angle, dipole orientation, and dielectric asymmetry, providing a deeper understanding of the factors governing the optical properties of layered TMDC heterostructures.
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