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Issue 16, 2017
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Anomalous enhancement of valley polarization in multilayer WS2 at room temperature

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Abstract

We probe the polarization of the “A” exciton photoluminescence from monolayer and multilayer WS2 at 10 K and 295 K under near-resonant and off-resonant conditions. The monolayer WS2 exhibits relatively low valley polarization, around 24% at 10 K and 8% at 295 K, while all multilayer WS2 samples show very high valley polarization, which is a more or less constant value of around 80% at 10 K under near-resonant excitation. At room temperature, it is observed experimentally that valley polarization in multilayer WS2 monotonously increases with shrinking of the indirect bandgap energy. The phonon-assisted intervalley scattering via the K–Γ–K(K′) valleys is identified as the primary valley polarization relaxation channel, which could be gradually suppressed as the thickness increases, leading to a valley polarization of up to 70% in multilayer WS2 (>3 unit layers).

Graphical abstract: Anomalous enhancement of valley polarization in multilayer WS2 at room temperature

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Supplementary files

Article information


Submitted
23 Jan 2017
Accepted
13 Mar 2017
First published
22 Mar 2017

Nanoscale, 2017,9, 5148-5154
Article type
Paper

Anomalous enhancement of valley polarization in multilayer WS2 at room temperature

H. Su, C. Wei, A. Deng, D. Deng, C. Yang and J. Dai, Nanoscale, 2017, 9, 5148 DOI: 10.1039/C7NR00554G

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