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arXiv 1003.3847cond-mat.mes-hallcond-mat.str-el
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通过Anderson杂质的非平衡输运:用运动方程方法探测标度律

Out of equilibrium transport through an Anderson impurity: Probing scaling laws within the equation of motion approach

C. A. Balseiro, Gonzalo Usaj, M. J. Sanchez

摘要:

利用运动方程方法研究了有限温度T下电子通过与金属引线耦合的量子杂质的非平衡输运。假设相互作用只发生在杂质中,并聚焦于无限Hubbard极限,我们计算了非平衡态密度和微分电导G_2(T,V),以检验几个标度律。我们发现G_2(T,V)/G_2(T,0)是eV/T_K和T/T_K的普适函数,T_K是Kondo温度。分析了面内磁场对微分电导中零偏异常分裂的影响。对于塞曼分裂Δ,计算出的微分电导峰分裂仅与Δ/T_K有关,在大电场下接近2Δ。除了传统的两个引线设置,我们还考虑其他配置,模仿最近的实验,即,嵌入在介观导线中的杂质和存在的第三个弱耦合的铅。在这些情况下,在微分电导中清楚地获得了近藤共振的双峰结构,而最高峰的幅度被示出为随着\ln(eV/T_K)而减小。这些结果的几个特点是在定性协议与最近的实验观察报告的量子点。

英文摘要:

We study non-equilibrium electron transport through a quantum impurity coupled to metallic leads using the equation of motion technique at finite temperature T. Assuming that the interactions are taking place solely in the impurity and focusing in the infinite Hubbard limit, we compute the out of equilibrium density of states and the differential conductance G_2(T,V) to test several scaling laws. We find that G_2(T,V)/G_2(T,0) is a universal function of both eV/T_K and T/T_K, being T_K the Kondo temperature. The effect of an in plane magnetic field on the splitting of the zero bias anomaly in the differential conductance is also analyzed. For a Zeeman splitting Δ, the computed differential conductance peak splitting depends only on Δ/T_K, and for large fields approaches the value of 2Δ. Besides the traditional two leads setup, we also consider other configurations that mimics recent experiments, namely, an impurity embedded in a mesoscopic wire and the presence of a third weakly coupled lead. In these cases, a double peak structure of the Kondo resonance is clearly obtained in the differential conductance while the amplitude of the highest peak is shown to decrease as \ln(eV/T_K). Several features of these results are in qualitative agreement with recent experimental observations reported on quantum dots.

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