Davydov splitting and excitonic resonance effects in Raman spectra of few-Layer MoSe2

Abstract

Raman spectra of few-layer MoSe2 were measured with 8 excitation energies. New peaks that appear only near resonance with various exciton states are analyzed, and the modes are assigned. The resonance profiles of the Raman peaks reflect the joint density of states for optical transitions, but the symmetry of the exciton wave functions leads to selective enhancement of the A1g mode at the A exciton energy and the shear mode at the C exciton energy. We also find Davydov splitting of intra-layer A1g, E1g, and A2u modes due to inter-layer interaction for some excitation energies near resonances. Furthermore, by fitting the spectral positions of inter-layer shear and breathing modes and Davydov splitting of intra-layer modes to a linear chain model, we extract the strength of the inter-layer interaction. We find that the second-nearest-neighbor inter-layer interaction amounts to about 30% of the nearest-neighbor interaction for both in-plane and out-of-plane vibrations.

45 pages, 19 figures, ACS Nano published (2016)

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• Stacking-Dependent Interlayer Phonons in 3R and 2H MoS${}_2$
• Observation of forbidden phonons and dark excitons by resonance Raman scattering in few-layer WS${}_2$
• Quantum interference effects in resonant Raman spectroscopy of single- and triple-layer MoTe${}_2$ from first principles
• Shear and breathing modes of layered materials
• Tunable layered-magnetism-assisted magneto-Raman effect in a two-dimensional magnet $\mathrm{Cr}{\mathrm{I}}_3$
• Excitonic Resonance Effects and Davydov Splitting in Circularly Polarized Raman Spectra of Few-Layer WSe2
• Electron-Phonon Coupling, Thermal Expansion Coefficient, Resonance Effect and Phonon Dynamics in High Quality CVD Grown Mono and Bilayer MoSe2
• Rigid-layer Raman-active modes in $N$-layer Transition Metal Dichalcogenides: interlayer force constants and hyperspectral Raman imaging
• Davydov Splitting, Resonance Effect and Phonon Dynamics in CVD grown Layered MoS2
• Raman Scattering with infrared excitation resonant with MoSe${}_2$ indirect band gap
• Raman Forbidden Layer-Breathing Modes in Layered Semiconductor Materials Activated by Phonon and Optical Cavity Effects
• A Se vacancy induced localized Raman mode in two-dimensional MoSe2 grown by CVD
• Synthesis and thermal stability of TMD thin films: A comprehensive XPS and Raman study
• Excitation energy dependence of Raman spectra of few-layer WS2