Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides

By H. Zeng, Gui-Bin Liu, J. Dai, Yajun Yan, Bairen Zhu, Ruicong He, Lu Xie, Shijie Xu, Xianhui Chen, W. Yao and 1 more. Scientific Reports, 2012

1,047 citations recorded by the source corpus.

We report systematic optical studies of WS2 and WSe2 monolayers and multilayers. The efficiency of second harmonic generation shows a dramatic even-odd oscillation with the number of layers, consistent with the presence (absence) of inversion symmetry in even-layer (odd-layer). Photoluminescence (PL) measurements show the crossover from an indirect band gap semiconductor at multilayers to a direct-gap one at monolayers. A hot luminescence peak (B) is observed at ~0.4 eV above the prominent band edge peak (A) in all samples. The magnitude of A-B splitting is independent of the number of layers and coincides with the spin-valley coupling strength in monolayers. Ab initio calculations show that this thickness independent splitting pattern is a direct consequence of the giant spin-valley coupling which fully suppresses interlayer hopping at valence band edge near K points because of the sign change of the spin-valley coupling from layer to layer in the 2H stacking order.

Subfields: Electronic, Optical and Magnetic Materials, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/128e5444081600b3d0fdec6b67f9559b3da35e69

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In Electronic, Optical and Magnetic Materials

1. Eli Yablonovitch
2. Roya Maboudian
3. G. Eda
4. Carlo Carraro
5. M. Potemski

In Materials Chemistry

1. Hongyi Yu
2. W. Yao
3. Xiaodong Xu
4. X. Cui
5. P. Tan
6. T. Yu
7. Chunxiao Cong
8. Yanlong Wang

Citations in the corpus

• Electronic structure, optical properties, and lattice dynamics in atomically thin indium selenide flakes (2014, methodology): “This is in contrast to observations in flakes based on layered transition‐ metal dichalcogenides, in which the orbital origin of states defining the bandgap differs from the bulk [17, 18, 44, 45, 49].”
• Optical properties of atomically thin transition metal dichalcogenides: observations and puzzles (2016, background): “[21] Zeng H, Liu G-B, Dai J, Yan Y, Zhu B, He R, Xie L, Xu S, Chen X, Yao W, Cui X.”