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arXiv 0907.5253cond-mat.mes-hall
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量子霍尔系统中纵向电导率与横向电导率的基本关系

Fundamental relation between longitudinal and transverse conductivities in the quantum Hall system

Akira Endo, Naomichi Hatano, Hiroaki Nakamura, Ryoen Shirasaki

摘要:

研究了量子霍尔系统电导率张量的对角分量($σ_{xx}$)和非对角分量($σ_{xy}$)之间的关系.我们计算的电导率组件的短程杂质电位使用的线性响应理论,采用一个近似,简单地取代自能的恒定值$-i \hbar /(2 τ)$与$τ$的散射时间。该近似等价于假设由于无序导致的朗道能级的加宽由具有宽度$Γ= \hbar /(2 τ)$的洛伦兹算符表示。解析公式得到的$σ_{xx}$和$σ_{xy}$在这个简单的近似在低温下的框架内。通过对$σ_{xx}$和$σ_{xy}$中前导项的分析,我们发现了$\mathrm{d}σ_{xy}/\mathrm{d}B$和$B σ_{xx}^2$之间的比例关系。在考虑到杂质势的长程性质而略作修改后,该关系式与低磁场区GaAs/AlGaAs二维电子系统中获得的实验结果定量一致,其中自旋分裂小到可以忽略不计。

英文摘要:

We investigate the relation between the diagonal ($σ_{xx}$) and off-diagonal ($σ_{xy}$) components of the conductivity tensor in the quantum Hall system. We calculate the conductivity components for a short-range impurity potential using the linear response theory, employing an approximation that simply replaces the self-energy by a constant value $-i \hbar /(2 τ)$ with $τ$ the scattering time. The approximation is equivalent to assuming that the broadening of a Landau level due to disorder is represented by a Lorentzian with the width $Γ= \hbar /(2 τ)$. Analytic formulas are obtained for both $σ_{xx}$ and $σ_{xy}$ within the framework of this simple approximation at low temperatures. By examining the leading terms in $σ_{xx}$ and $σ_{xy}$, we find a proportional relation between $\mathrm{d}σ_{xy}/\mathrm{d}B$ and $B σ_{xx}^2$. The relation, after slight modification to account for the long-range nature of the impurity potential, is shown to be in quantitative agreement with experimental results obtained in the GaAs/AlGaAs two-dimensional electron system at the low magnetic-field regime where spin splitting is negligibly small.

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