Photon energy dependence of angle-resolved photoemission spectroscopy in graphene
Photon energy dependence of angle-resolved photoemission spectroscopy in graphene
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DOI：
10.1103/physrevb.92.195148
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发表时间：
2015-11-24
影响因子：
3.7
通讯作者：
Saito, Riichiro
中科院分区：
文献类型：
--
作者：
Ayria, Pourya;Nugraha, Ahmad R. T.;Saito, Riichiro
从理论和实验上研究了石墨烯角分辨光电子能谱（ARPES）的光子能量依赖性。通过施加具有大约46 eV的能量的光，我们发现相对于s分支（被s偏振光增亮的那些），p分支（被p偏振光增亮的ARPES光谱）的石墨烯的ARPES相对强度意外增加。通过第一性原理计算解释了p分支强度增强的起源，其中我们显示了（1）作为激发电子的终态能量的函数的光学偶极矢量，（2）作为入射光角度的函数的吸收强度，以及（3）初始和终态的对称性。计算结果表明，在46 eV附近的激发电子的偶极矢量在石墨烯表面的法线方向上比在石墨烯平面内有一个特别大的分量，这可能是p支强度增强的主要原因.
The photon energy dependence of angle-resolved photoemission spectroscopy (ARPES) in graphene is investigated experimentally and theoretically. By applying light with energy of around 46 eV, we found an unexpected increase in the ARPES relative intensity of graphene for the p branch (ARPES spectra brightened by the p-polarized light) with respect to the s branch (those brightened by the s-polarized light). The origin of the enhanced p-branch intensity is explained by first-principles calculations, in which we show (1) the optical dipole vector as a function of final-state energies of the excited electron, (2) the absorption intensity as a function of the incident light angle, and (3) the symmetry of the initial and the final states. The calculated results imply that the dipole vector of the excited electron near 46 eV has an exceptionally large component in the normal direction of the graphene surface compared to that within the graphene plane, which could be the main reason for the enhancement of the p-branch intensity.