Tuning the Fröhlich exciton-phonon scattering in monolayer MoS 2

Charge carriers in semiconducting transition metal dichalcogenides possess a valley degree of freedom that allows for optoelectronic applications based on the momentum of excitons. At elevated temperatures, scattering by phonons limits valley polarization, making a detailed knowledge about strength...

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Bibliographic Details
Published in:Nature communications 2019-12, Vol.10 (1), p.807
Main Authors: Miller, Bastian, Lindlau, Jessica, Bommert, Max, Neumann, Andre, Yamaguchi, Hisato, Holleitner, Alexander, Högele, Alexander, Wurstbauer, Ursula
Format: Article
Language:English
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Summary:Charge carriers in semiconducting transition metal dichalcogenides possess a valley degree of freedom that allows for optoelectronic applications based on the momentum of excitons. At elevated temperatures, scattering by phonons limits valley polarization, making a detailed knowledge about strength and nature of the interaction of excitons with phonons essential. In this work, we directly access exciton-phonon coupling in charge tunable single layer MoS devices by polarization resolved Raman spectroscopy. We observe a strong defect mediated coupling between the long-range oscillating electric field induced by the longitudinal optical phonon in the dipolar medium and the exciton. This so-called Fröhlich exciton phonon interaction is suppressed by doping. The suppression correlates with a distinct increase of the degree of valley polarization up to 20% even at elevated temperatures of 220 K. Our result demonstrates a promising strategy to increase the degree of valley polarization towards room temperature valleytronic applications.
ISSN:2041-1723
DOI:10.1038/s41467-019-08764-3