Please use this identifier to cite or link to this item: https://hdl.handle.net/10356/144678
Title: Unveiling exceptionally robust valley contrast in AA- and AB-stacked bilayer WS2
Authors: Wang, Yanlong
Cong, Chunxiao
Shang, Jingzhi
Eginligil, Mustafa
Jin, Yuqi
Li, Gang
Chen, Yu
Peimyoo, Namphung
Yu, Ting
Keywords: Science::Physics
Issue Date: 2019
Source: Wang, Y., Cong, C., Shang, J., Eginligil, M., Jin, Y., Li, G., ... Yu, T. (2019). Unveiling exceptionally robust valley contrast in AA- and AB-stacked bilayer WS2. Nanoscale Horizons, 4(2), 396-403. doi:10.1039/C8NH00306H
Project: RG199/17
Journal: Nanoscale Horizons
Abstract: Valleytronics is a particularly interesting field that employs the valley degree of freedom for information manipulation. The fascinating prospects for realizing valleytronic devices have inspired persistent efforts towards exploring material systems with robust valley polarization. Monolayer transition metal dichalcogenides (TMDs) obey the well-known valley-dependent selection rule as a result of their inversion asymmetry. However, for inversionsymmetric bilayer tungsten-based TMDs, highly selective valley polarization has been surprisingly observed and is not yet fully understood. Here we systematically study the origin of the anomalously high valley polarization in bilayer WS2 by temperaturedependent polarization-resolved photoluminescence measurements. It is found that acoustic phonons play a critical role in the valley polarization of bilayer WS2. For some WS2 bilayers with relatively small intensity ratios of indirect to direct bandgap emission, acoustic phonons could remarkably assist the intervalley scattering process and smear the valley contrast. On the other hand, in other bilayers, which show obvious indirect band gap emission, the indirect optical transition process depletes the phonon mode at the K point dramatically and results in anomalously robust valley polarization in bilayer WS2. These results help recognize the crucial role of electron–phonon coupling in intervalley relaxation in bilayer WS2 and provide new insights into the future design of valleytronic devices based on two-dimensional TMDs.
URI: https://hdl.handle.net/10356/144678
ISSN: 2051-6347
DOI: 10.1039/C8NH00306H
Rights: © 2018 Royal Society of Chemistry. All rights reserved. This paper was published in Nanoscale Horizons and is made available with permission of Royal Society of Chemistry.
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:SPMS Journal Articles

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