期刊
NATURE COMMUNICATIONS
卷 8, 期 -, 页码 -出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/ncomms14927
关键词
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资金
- ERC grant [306719]
- ITN Spin-NANO Marie Sklodowska-Curie grant [676108]
- ANR MoS2ValleyControl
- Programme Investissements d Avenir [ANR-11-IDEX-0002-02, ANR-10-LABX-0037-NEXT]
- LIA CNRS-Ioffe RAS ILNACS
- RFBR
- Russian Federation President [MD-1555.2017.2]
- Dynasty Foundation
- Elemental Strategy Initiative
- JSPS KAKENHI [JP26248061, JP15K21722, JP25106006]
- Grants-in-Aid for Scientific Research [25107004, 15K21722] Funding Source: KAKEN
Excitons, Coulomb bound electron-hole pairs, are composite bosons and their interactions in traditional semiconductors lead to condensation and light amplification. The much stronger Coulomb interaction in transition metal dichalcogenides such as WSe2 monolayers combined with the presence of the valley degree of freedom is expected to provide new opportunities for controlling excitonic effects. But so far the bosonic character of exciton scattering processes remains largely unexplored in these two-dimensional materials. Here we show that scattering between B-excitons and A-excitons preferably happens within the same valley in momentum space. This leads to power dependent, negative polarization of the hot B- exciton emission. We use a selective upconversion technique for efficient generation of B-excitons in the presence of resonantly excited A-excitons at lower energy; we also observe the excited A-excitons state 2s. Detuning of the continuous wave, low-power laser excitation outside the A-exciton resonance (with a full width at half maximum of 4 meV) results in vanishing upconversion signal.
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