Sub-100 fs formation of dark excitons in monolayer WS2

• Verfasst von: Kolesnichenko, Pavel V. [VerfasserIn]
• Verfasst von: Wittenbecher, Lukas [VerfasserIn]
• Verfasst von: Zhang, Qianhui [VerfasserIn]
• Verfasst von: Teh, Run Yan [VerfasserIn]
• Verfasst von: Babu, Chandni [VerfasserIn]
• Verfasst von: Fuhrer, Michael S. [VerfasserIn]
• Verfasst von: Mikkelsen, Anders [VerfasserIn]
• Verfasst von: Zigmantas, Donatas [VerfasserIn]
• Titel: Sub-100 fs formation of dark excitons in monolayer WS2
• Verf.angabe: Pavel V. Kolesnichenko, Lukas Wittenbecher, Qianhui Zhang, Run Yan Teh, Chandni Babu, Michael S. Fuhrer, Anders Mikkelsen, and Donatas Zigmantas
• Jahr: 2024
• Umfang: 8 S.
• Illustrationen: Illustrationen, Diagramme
• Fussnoten: Online veröffentlicht: 8. November 2024 ; Gesehen am 25.06.2025
• Titel Quelle: Enthalten in: Nano letters
• Ort Quelle: Washington, DC : ACS Publ., 2001
• Jahr Quelle: 2024
• Band/Heft Quelle: 24(2024), 46, Seite 14663-14670
• ISSN Quelle: 1530-6992
• DOI: doi:10.1021/acs.nanolett.4c03807
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 192907705X

Abstract

Two-dimensional semiconducting transition metal dichalcogenides are promising materials for optoelectronic applications due to their strongly bound excitons. While bright excitons have been thoroughly scrutinized, dark excitons have been much less investigated, as they are not directly observable with far-field spectroscopy. However, with their nonzero momenta, dark excitons are significant for applications requiring long-range transport or coupling to external fields. We access such dark excitons in WS2 monolayer using transient photoemission electron microscopy with subdiffraction limited spatial resolution (75 nm) and exceptionally high temporal resolution (13 fs). Image time series of the monolayer are recorded at several different fluences. We directly observe the ultrafast formation of dark K-Λ excitons occurring within 14-50 fs and follow their subsequent picosecond decay. We distinguish exciton dynamics between the monolayer’s interior and edges and conclude that the picosecond-scale evolution of dark excitations is defect-mediated while intervalley scattering is not affected by the defects.