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arXiv 0810.5719cond-mat.mtrl-scicond-mat.mes-hall
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碳纳米管中自旋极化输运的磁电阻效应

Magnetoresistance in Spin-Polarized Transport through a Carbon Nanotube

Tae-Suk Kim, Choong-Ki Lee, Hyun-Woo Lee, B. C. Lee, K. Rhie

摘要:

本文报道了我们对有限长碳纳米管中自旋极化输运的磁电阻效应的理论研究。通过改变碳纳米管的费米能级和碳纳米管与两个铁磁电极的耦合强度,研究了碳纳米管的电导和磁电阻。由于通过有限CNT中的离散能级的共振输运,电导和MR作为CNT费米能的函数振荡。MR在电导谷处达到峰值,并在电导峰附近下降。当耦合到两个FM电极是不对称的,MR下降成为负的下一个相当强的不对称性。当耦合或多或少对称时,除了非常强的耦合情况之外,MR骤降保持为正。在强耦合情况下,谱线展宽显著,通过CNT中相邻能级的输运通道相互干扰,导致负MR。

英文摘要:

We report on our theoretical study of the magnetoresistance in spin polarized transport through a finite carbon nanotube (CNT). Varying the Fermi energy of a CNT and the relative strength of couplings to two ferromagnetic (FM) electrodes, we studied the conductance as well as the magnetoresistance (MR). Due to resonant transport through discrete energy levels in a finite CNT, the conductance and MR are oscillating as a function of the CNT Fermi energy. The MR is peaked at the conductance valleys and dipped close to the conductance peaks. When couplings to two FM electrodes are asymmetric, the MR dips become negative under a rather strong asymmetry. When couplings are more or less symmetric, the MR dips remain positive except for a very strong coupling case. Under strong coupling case, the line broadening is significant and transport channels through neighboring energy levels in a CNT interfere with each other, leading to the negative MR.

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