Twist angle dependent interlayer transfer of valley polarization from excitons to free charge carriers in WSe2/MoSe2 heterobilayers

Transition metal dichalcogenides (TMDs) have attracted much attention in the fields of valley- and spintronics due to their property of forming valley-polarized excitons when illuminated by circularly polarized light. In TMD-heterostructures it was shown that these electron-hole pairs can scatter in...

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Published in:NPJ 2D materials and applications 2023-08, Vol.7 (1), p.58-10, Article 58
Main Authors: Volmer, Frank, Ersfeld, Manfred, Faria Junior, Paulo E., Waldecker, Lutz, Parashar, Bharti, Rathmann, Lars, Dubey, Sudipta, Cojocariu, Iulia, Feyer, Vitaliy, Watanabe, Kenji, Taniguchi, Takashi, Schneider, Claus M., Plucinski, Lukasz, Stampfer, Christoph, Fabian, Jaroslav, Beschoten, Bernd
Format: Article
Language:English
Subjects:
639/766/1130/2798
639/766/119/1000/1018
639/766/119/1001
639/766/930/527
639/925/930/527
Chemistry and Materials Science
Circular polarization
Copper
Current carriers
Energy
Excitons
Heterostructures
Holes (electron deficiencies)
Interlayers
Materials Science
Measurement techniques
Molybdenum compounds
Nanotechnology
Optoelectronic devices
Physics
Polarized light
Spintronics
Surfaces and Interfaces
Thin Films
Transition metal compounds
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Summary:Transition metal dichalcogenides (TMDs) have attracted much attention in the fields of valley- and spintronics due to their property of forming valley-polarized excitons when illuminated by circularly polarized light. In TMD-heterostructures it was shown that these electron-hole pairs can scatter into valley-polarized interlayer exciton states, which exhibit long lifetimes and a twist-angle dependence. However, the question how to create a valley polarization of free charge carriers in these heterostructures after a valley selective optical excitation is unexplored, despite its relevance for opto-electronic devices. Here, we identify an interlayer transfer mechanism in twisted WSe 2 /MoSe 2 heterobilayers that transfers the valley polarization from excitons in WSe 2 to free charge carriers in MoSe 2 with valley lifetimes of up to 12 ns. This mechanism is most efficient at large twist angles, whereas the valley lifetimes of free charge carriers are surprisingly short for small twist angles, despite the occurrence of interlayer excitons.
ISSN:2397-7132
2397-7132
DOI:10.1038/s41699-023-00420-1