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Intervalley scattering by acoustic phonons in two-dimensional MoS2 revealed by double-resonance Raman spectroscopy.
Nature Communications ( IF 14.7 ) Pub Date : 2017-03-09 , DOI: 10.1038/ncomms14670 Bruno R Carvalho 1 , Yuanxi Wang 2 , Sandro Mignuzzi 3, 4 , Debdulal Roy 3, 4 , Mauricio Terrones 2, 5, 6 , Cristiano Fantini 1 , Vincent H Crespi 2 , Leandro M Malard 1 , Marcos A Pimenta 1
Nature Communications ( IF 14.7 ) Pub Date : 2017-03-09 , DOI: 10.1038/ncomms14670 Bruno R Carvalho 1 , Yuanxi Wang 2 , Sandro Mignuzzi 3, 4 , Debdulal Roy 3, 4 , Mauricio Terrones 2, 5, 6 , Cristiano Fantini 1 , Vincent H Crespi 2 , Leandro M Malard 1 , Marcos A Pimenta 1
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Double-resonance Raman scattering is a sensitive probe to study the electron-phonon scattering pathways in crystals. For semiconducting two-dimensional transition-metal dichalcogenides, the double-resonance Raman process involves different valleys and phonons in the Brillouin zone, and it has not yet been fully understood. Here we present a multiple energy excitation Raman study in conjunction with density functional theory calculations that unveil the double-resonance Raman scattering process in monolayer and bulk MoS2. Results show that the frequency of some Raman features shifts when changing the excitation energy, and first-principle simulations confirm that such bands arise from distinct acoustic phonons, connecting different valley states. The double-resonance Raman process is affected by the indirect-to-direct bandgap transition, and a comparison of results in monolayer and bulk allows the assignment of each Raman feature near the M or K points of the Brillouin zone. Our work highlights the underlying physics of intervalley scattering of electrons by acoustic phonons, which is essential for valley depolarization in MoS2.
中文翻译：
双共振拉曼光谱揭示了二维 MoS2 中声学声子的谷间散射。
双共振拉曼散射是研究晶体中电子-声子散射路径的灵敏探针。对于半导体二维过渡金属二硫属化物，双共振拉曼过程涉及布里渊区的不同谷和声子，目前尚未完全了解。在这里，我们提出了结合密度泛函理论计算的多能量激发拉曼研究，揭示了单层和块状 MoS 2中的双共振拉曼散射过程。结果表明，当改变激发能量时，一些拉曼特征的频率会发生变化，第一原理模拟证实这些频带来自不同的声学声子，连接不同的谷态。双共振拉曼过程受到间接到直接带隙跃迁的影响，单层和块体结果的比较允许在布里渊区的 M 或 K 点附近分配每个拉曼特征。我们的工作强调了声声子对电子进行层间散射的基本物理原理，这对于 MoS 2中的谷去极化至关重要。
更新日期：2017-03-11
中文翻译：
双共振拉曼光谱揭示了二维 MoS2 中声学声子的谷间散射。
双共振拉曼散射是研究晶体中电子-声子散射路径的灵敏探针。对于半导体二维过渡金属二硫属化物，双共振拉曼过程涉及布里渊区的不同谷和声子，目前尚未完全了解。在这里，我们提出了结合密度泛函理论计算的多能量激发拉曼研究，揭示了单层和块状 MoS 2中的双共振拉曼散射过程。结果表明，当改变激发能量时，一些拉曼特征的频率会发生变化，第一原理模拟证实这些频带来自不同的声学声子，连接不同的谷态。双共振拉曼过程受到间接到直接带隙跃迁的影响，单层和块体结果的比较允许在布里渊区的 M 或 K 点附近分配每个拉曼特征。我们的工作强调了声声子对电子进行层间散射的基本物理原理，这对于 MoS 2中的谷去极化至关重要。
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