Fermi energy dependence of first- and second-order Raman spectra in graphene: Kohn anomaly and quantum interference effect
Fermi energy dependence of first- and second-order Raman spectra in graphene: Kohn anomaly and quantum interference effect
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DOI：
10.1103/physrevb.94.075104
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发表时间：
2016-08-02
影响因子：
3.7
通讯作者：
Saito, Riichiro
中科院分区：
文献类型：
--
作者：
Hasdeo, Eddwi H.;Nugraha, Ahmad R. T.;Saito, Riichiro
一阶和二阶拉曼光谱的强度计算为费米能量的函数。我们发现，一阶拉曼光谱中的科恩反常效应，即声子频率重整化，源于带间电子空穴激发的声子重整化，而在二阶拉曼光谱中，带间和带内电子空穴激发之间发生了竞争。通过此计算，我们确认了拉曼峰值频率作为一阶和二阶拉曼光谱费米能量的函数存在不同的色散行为，正如在之前的一些实验中观察到的那样。此外，拉曼强度的计算结果敏感地依赖于一阶和二阶拉曼光谱的费米能量，表明量子干涉效应的存在。电子-声子矩阵元素在作为费米能量函数的组合（泛音）声子模式的强度增加（减少）中起着重要作用。
Intensities of the first-and the second-order Raman spectra are calculated as a function of the Fermi energy. We show that the Kohn anomaly effect, i.e., phonon frequency renormalization, in the first-order Raman spectra originates from the phonon renormalization by the interband electron-hole excitation, whereas in the second-order Raman spectra, a competition between the interband and intraband electron-hole excitations takes place. By this calculation, we confirm the presence of different dispersive behaviors of the Raman peak frequency as a function of the Fermi energy for the first-and the second-order Raman spectra, as observed in some previous experiments. Moreover, the calculated results of the Raman intensity sensitively depend on the Fermi energy for both the first-and the second-order Raman spectra, indicating the presence of the quantum interference effect. The electron-phonon matrix element plays an important role in the intensity increase ( decrease) of the combination ( overtone) phonon modes as a function of the Fermi energy.