Excitons and plasmons of graphene nanoribbons in infrared frequencies in an effective-mass approximation
Excitons and plasmons of graphene nanoribbons in infrared frequencies in an effective-mass approximation
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DOI：
10.1103/physrevb.102.155409
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发表时间：
2020-10
影响因子：
3.7
通讯作者：
S. Uryu
中科院分区：
文献类型：
--
作者：
S. Uryu
在有效质量近似下，从理论上全面研究了电子-电子相互作用对石墨烯纳米带光学响应的影响。在没有掺杂和掺杂的扶手形纳米带和之字形纳米带的光学吸收光谱中，电子和空穴的束缚态激子和等离子体激子表现为各种突出的峰。对于平行于纳米带的光偏振，由于与暗激子的相互作用，高能激子峰分裂，而暗激子的光学跃迁是被禁止的。对于垂直于纳米带极化的光，在未掺杂的半导体扶手椅纳米带中，激子峰出现适度，而在掺杂扶手椅纳米带和之字形纳米带中，只有当费米能量跨越至少两个能带时，由于狄拉克电子的性质，才会出现较大的等离子体峰。这些峰可以分配给特定的光学跃迁的能带。通过适当的能量和波矢量缩放，各种纳米带中激子和等离子体产生的光吸收峰与碳纳米管的光吸收峰近似对应。
Effects of electron-electron interactions on the optical response of graphene nanoribbons are theoretically investigated in an effective-mass approximation in a comprehensive manner. In optical absorption spectra of armchair and zigzag nanoribbons without and with doping, excitons, which are bound states of electrons and holes, and plasmons manifest themselves as various prominent peaks. For light polarized parallel to nanoribbons, exciton peaks at high energies split because of interactions with dark excitons, to which optical transition is prohibited. For light polarized perpendicular to nanoribbons, in nondoped semiconducting armchair nanoribbons, moderate exciton peaks appear while in doped armchair and zigzag nanoribbons, only when the Fermi energy crosses at least two energy bands, large plasmon peaks occur because of a nature of Dirac electrons. These peaks can be assigned to specific optical transitions in energy bands. The optical absorption peaks arising from the excitons and plasmons in a wide range of categories of nanoribbons approximately correspond to those of carbon nanotubes by appropriate scaling of energy and the wave vector.