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arXiv 1012.0526cond-mat.mes-hall
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少层石墨烯中电荷和自旋输运的比较

Comparison between charge and spin transport in few layer graphene

T. Maassen, F. K. Dejene, M. H. D. Guimarães, C. Józsa, B. J. van Wees

摘要:

对几层石墨烯(FLG)的输运测量是重要的,因为它们在作为真正的二维材料的单层石墨烯(SLG)的性质和石墨的三维本体性质之间进行插值。在这篇文章中,我们提出了四探针的本地电荷输运和非本地自旋阀和自旋进动测量横向自旋场效应晶体管(FET)上的FLG。我们系统地研究了电荷和自旋输运性质取决于层数和电子背门的设备。我们解释的电荷传输测量考虑到散射电位的筛选,并使用结果来理解自旋数据。测量的样本厚度在3到20层之间,我们在分析中包括了SLG的早期测量结果以供比较。在我们的室温自旋输运测量,我们设法观察自旋信号的距离高达10 μ m和测量自旋弛豫时间高达τ_s ~500 ps,约4倍以上的SLG。我们用区域折叠法计算了FLG的态密度,由电阻的平方R_S确定了电荷扩散系数D_C。得到的D_C和自旋扩散系数D_S显示出相似的值,并且仅弱地依赖于层的数目和栅极感生的载流子。我们讨论了这对识别自旋弛豫机制的影响。

英文摘要:

Transport measurements on few layer graphene (FLG) are important as they interpolate between the properties of single layer graphene (SLG) as a true 2-dimensional material and the 3-dimensional bulk properties of graphite. In this article we present 4-probe local charge transport and non-local spin valve and spin precession measurements on lateral spin field-effect transistors (FET) on FLG. We study systematically the charge and spin transport properties depending on the number of layers and the electrical back gating of the device. We explain the charge transport measurements by taking the screening of scattering potentials into account and use the results to understand the spin data. The measured samples are between 3 and 20 layers thick and we include in our analysis our earlier results of the measurements on SLG for comparison. In our room temperature spin transport measurements we manage to observe spin signals over distances up to 10 u m and measure spin-relaxation times up to tau_s ~500 ps, about 4 times higher than in SLG. We calculate the density of states (DOS) of FLG using a zone-folding scheme to determine the charge diffusion coefficient D_C from the square resistance R_S. The resulting D_C and the spin diffusion coefficient D_S show similar values and depend only weakly on the number of layers and gate induced charge carriers. We discuss the implications of this on the identification of the spin-relaxation mechanism.

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