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arXiv 1707.08286cond-mat.dis-nncond-mat.mes-hallcond-mat.stat-mech
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安德森局域化转变附近的热电性

Thermoelectricity near Anderson localization transitions

Kaoru Yamamoto, Amnon Aharony, Ora Entin-Wohlman, Naomichi Hatano

摘要:

在三维空间中分析了一个和两个安德森局域化阈值附近的电子热电系数。对于一个单一的迁移率边缘,我们纠正和扩展以前的研究,并找到通用的近似,允许推导出临界指数的零温度电导率从热电测量。特别是,我们发现,在非零低温下的塞贝克系数和热电效率可以是非常大的“绝缘”侧,化学势低于(零温度)本地化阈值。校正的领先的幂律奇异性的零温度电导率示出引入非通用的温度相关的校正,否则通用的功能,描述的塞贝克系数,品质因数和Wiedemann-Franz比。接下来,热电系数示出有有趣的依赖于系统的大小。而塞贝克系数随着尺寸减小而减小,品质因数先减小后增大,而Wiedemann-Franz比随着尺寸减小而先增大后减小。因此,小的(但有限的)样本可以具有更大的热电效率。在最后一部分中,我们研究了具有一对局域边的系统中的热电性,这是随机系统中电子能带中心附近的普遍情况。随着无序度的增加,两个阈值彼此接近,然后塞贝克系数和品质因数显著增加,正如从Mahan和Sofo [J.D. Mahan和J.O. Sofo,Proc. Natl. Acad. Sci. U.S.A.93,7436(1996)],用于窄能量范围的零温度金属行为。

英文摘要:

The electronic thermoelectric coefficients are analyzed in the vicinity of one and two Anderson localization thresholds in three dimensions. For a single mobility edge, we correct and extend previous studies, and find universal approximants which allow to deduce the critical exponent for the zero-temperature conductivity from thermoelectric measurements. In particular, we find that at non-zero low temperatures the Seebeck coefficient and the thermoelectric efficiency can be very large on the "insulating" side, for chemical potentials below the (zero-temperature) localization threshold. Corrections to the leading power-law singularity in the zero-temperature conductivity are shown to introduce non-universal temperature-dependent corrections to the otherwise universal functions which describe the Seebeck coefficient, the figure of merit and the Wiedemann-Franz ratio. Next, the thermoelectric coefficients are shown to have interesting dependences on the system size. While the Seebeck coefficient decreases with decreasing size, the figure of merit first decreases but then increases, while the Wiedemann-Franz ratio first increases but then decreases as the size decreases. Small (but finite) samples may thus have larger thermoelectric efficiencies. In the last part we study thermoelectricity in systems with a pair of localization edges, the ubiquitous situation in random systems near the centers of electronic energy bands. As the disorder increases, the two thresholds approach each other, and then the Seebeck coefficient and the figure of merit increase significantly, as expected from the general arguments of Mahan and Sofo [J. D. Mahan and J. O. Sofo, Proc. Natl. Acad. Sci. U.S.A. 93, 7436 (1996)] for a narrow energy-range of the zero-temperature metallic behavior.

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