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Decay and frequency shift of both intervalley and intravalley phonons in graphene: Dirac-cone migration

colorstone 添加于 2012-11-30 14:03 | 1290 次阅读 | 0 个评论

作者
Sasaki K-ichi, Kato K, Tokura Y, Suzuki S, Sogawa T
摘要
By considering analytical expressions for the self-energies of intervalley and intravalley phonons in graphene, we describe the behavior of D, 2D, and D^′ Raman bands with changes in doping (μ) and light-excitation energy (E_L). Comparing the self-energy with the observed μ dependence of the 2D bandwidth, we estimate the wave vector q of the constituent intervalley phonon at ℏvq≃E_L/1.6 (v is the electron\'s Fermi velocity) and conclude that the self-energy makes a major contribution (60%) to the dispersive behavior of the D and 2D bands. The estimate of q is based on a concept of shifted Dirac cones in which the resonance decay of a phonon satisfying q>ω/v (ω is the phonon frequency) into an electron-hole pair is suppressed when μ<(ℏvq−ℏω)/2. We highlight the fact that the decay of an intervalley (and intravalley longitudinal optical) phonon with q=ω/v is strongly suppressed by electron-phonon coupling at an arbitrary μ. This feature is in contrast with the divergent behavior of an intravalley transverse optical phonon, which bears a close similarity to the polarization function relevant to plasmons.
详细资料
- 文献种类: Journal Article
- 期刊名称: Physical Review B
- 期刊缩写: Phys. Rev. B
- 期卷页: 2012年第86卷第20期
- ISBN: 1098-0121
学科领域工程技术 » 材料科学
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