Helicity resolved Raman scattering of MoS2, MoSe2, WS2 and WSe2 atomic layers

Abstract

The two-fold valley degeneracy in two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDCs) (Mo,W)(S,Se)2 is suitable for "valleytronics", the storage and manupulation of information utilizing the valley degree of freedom. The conservation of luminescent photon helicity in these 2D crystal monolayers has been widely regarded as a benchmark indicator for charge carrier valley polarization. Here we perform helicity-resolved Raman scattering of the TMDC atomic layers. In drastic contrast to luminescence, the dominant first-order zone-center Raman bands, including the low energy breathing and shear modes as well as the higher energy optical phonons, are found to either maintain or completely switch the helicity of incident photons. These experimental observations, in addition to providing a useful tool for characterization of TMDC atomic layers, shed new light on the connection between photon helicity and valley polarization.

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• Superior valley polarization and coherence of 2s excitons in monolayer WSe2
• Recent Progress of Heterostructures Based on Two Dimensional Materials and Wide Bandgap Semiconductors
• Low-frequency Raman scattering in WSe${}_2$-MoSe${}_2$ heterobilayers: Evidence for atomic reconstruction
• Chiral phonons in honeycomb sublattice of layered CoSn-like compounds
• The optical signature of few-layer ReSe${}_2$
• Up- and Down-Conversion between Intra- and Inter-Valley Excitons in Waveguide Coupled Monolayer WSe2
• Direct Observation of Intravalley Phonon Scattering of 2s Excitons in MoSe${}_2$ and WSe${}_2$ Monolayers
• Exciton-activated effective phonon magnetic moment in monolayer MoS2
• Low-frequency Raman signature of Ag-intercalated few-layer MoS${}_2$
• Helicity resolved Raman spectroscopy of mono- and a few-layers thick PtSe${}_2$
• Phonon pseudoangular momentum in $\alpha$-MoO${}_3$
• Directing Monolayer Tungsten Disulfide Photoluminescence using a Bent Plasmonic Nanowire on a Mirror Cavity
• Two-Dimensional Transition Metal Dichalcogenides-Based Counter Electrodes for Dye-Sensitized Solar Cells
• Excitation energy dependence of Raman spectra of few-layer WS2
• Kolmogorov-Crespi Potential For Multilayer Transition Metal Dichalcogenides: Capturing Structural Transformations In Moiré Superlattices