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arXiv 1503.07764cond-mat.mes-hall
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弯曲碳纳米管中的自旋-轨道相互作用:共振自旋跃迁

Spin-orbit interaction in bent carbon nanotubes: resonant spin transitions

E. N. Osika, B. Szafran

摘要:

针对弯曲碳纳米管中形成$π$键的电子,提出了一种有效的紧束缚哈密顿量.我们占弯曲的CNT和内在的自旋轨道相互作用,引入混合的$π$和$σ$键之间的$p_z$轨道沿CNT。该效应有助于SO耦合的主要来源-石墨烯平面折叠成纳米管。讨论了双量子点中SO耦合对共振单电子自旋和电荷跃迁的弯曲贡献。我们报告说,虽然弯曲相关的SO耦合的影响是弱的能谱,它产生了显着的增加由外部电场驱动的自旋跃迁速率。我们发现,由交替电场驱动的自旋翻转跃迁通常有较大的速率时,伴随着电荷从一个点到另一个。自旋翻转跃迁速率是驱动振幅的非单调函数,因为它们被更强的自旋守恒电荷跃迁所掩盖。我们证明,分数共振-对应的多光子跃迁的原子在强激光场-发生在电控纳米器件已经在中等交流振幅-可以用来维持自旋翻转过渡。

英文摘要:

We develop an effective tight-binding Hamiltonian for spin-orbit (SO) interaction in bent carbon nanotubes (CNT) for the electrons forming the $π$ bonds between the nearest neighbor atoms. We account for the bend of the CNT and the intrinsic spin-orbit interaction which introduce mixing of $π$ and $σ$ bonds between the $p_z$ orbitals along the CNT. The effect contributes to the main origin of the SO coupling--the folding of the graphene plane into the nanotube. We discuss the bend-related contribution of the SO coupling for resonant single-electron spin and charge transitions in a double quantum dot. We report that although the effect of the bend-related SO coupling is weak for the energy spectra, it produces a pronounced increase of the spin transition rates driven by an external electric field. We find that spin-flipping transitions driven by alternate electric fields have usually larger rates when accompanied by charge shift from one dot to the other. Spin-flipping transition rates are non-monotonic functions of the driving amplitude since they are masked by stronger spin-conserving charge transitions. We demonstrate that the fractional resonances--counterparts of multiphoton transitions for atoms in strong laser fields--occurring in electrically controlled nanodevices already at moderate ac amplitudes--can be used to maintain the spin-flip transitions.

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