Osika E N, Szafran B
AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059 Kraków, Poland.
J Phys Condens Matter. 2015 Nov 4;27(43):435301. doi: 10.1088/0953-8984/27/43/435301. Epub 2015 Oct 8.
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.
我们为弯曲碳纳米管（CNT）中形成最近邻原子间π键的电子的自旋轨道（SO）相互作用开发了一种有效的紧束缚哈密顿量。我们考虑了碳纳米管的弯曲以及本征自旋轨道相互作用，这会导致沿碳纳米管的p(z)轨道之间的π键和σ键发生混合。这种效应是SO耦合的主要起源之一——石墨烯平面折叠成纳米管。我们讨论了SO耦合与双量子点中共振单电子自旋和电荷跃迁相关的弯曲贡献。我们报告称，尽管与弯曲相关的SO耦合对能谱的影响较弱，但它会使外部电场驱动的自旋跃迁速率显著增加。我们发现，由交变电场驱动的自旋翻转跃迁在伴随着电荷从一个量子点转移到另一个量子点时，通常具有更大的速率。自旋翻转跃迁速率是驱动幅度的非单调函数，因为它们被更强的自旋守恒电荷跃迁所掩盖。我们证明，在电控纳米器件中，即使在中等交流幅度下就会出现的分数共振——强激光场中原子多光子跃迁的对应物——可用于维持自旋翻转跃迁。
