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arXiv 1210.7838cond-mat.str-elcond-mat.dis-nn
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非平衡二维电子系统中的电导噪声

Conductance noise in an out-of-equilibrium two-dimensional electron system

Ping V. Lin, Xiaoyan Shi, J. Jaroszynski, Dragana Popović

摘要:

对Si中二维电子系统(2DES)在低温(T)下的电导噪声进行了研究,发现当载流子密度n_s固定时,在高温下从平衡态冷却后,出现了大的非高斯噪声.当n_s<n_g(n_g -玻璃化转变密度)时观察到这种行为,其表示当T->0时2DES的平衡下降。在低T下,密度改变一个小值Δn_s的协议对噪声功率谱产生相同的结果。然而,对涨落的非高斯概率密度函数(PDF)的详细分析表明,Δn_s具有与ΔT性质不同且更为显著的效应,这表明Δn_s由于库仑相互作用而引起系统自由能景观的强烈变化。从第三,等待时间(t_w)协议,其中n_s在t_w期间临时改变了大量的结果表明,非高斯PDF表现出历史依赖性和高斯分布的演变,随着系统的年龄和慢慢接近平衡。通过计算功率谱和高阶统计量的噪声测量在一个广泛的范围内的施加的电压偏置,它是建立的非高斯噪声观察到的欧姆或线性响应的制度,即它不是由施加的偏压。

英文摘要:

A study of the conductance noise in a two-dimensional electron system (2DES) in Si at low temperatures (T) reveals the onset of large, non-Gaussian noise after cooling from an equilibrium state at a high T with a fixed carrier density n_s. This behavior, which signifies the falling out of equilibrium of the 2DES as T->0, is observed for n_s<n_g (n_g - glass transition density). A protocol where density is changed by a small value Δn_s at low T produces the same results for the noise power spectra. However, a detailed analysis of the non-Gaussian probability density functions (PDFs) of the fluctuations reveals that Δn_s has a qualitatively different and more dramatic effect than ΔT, suggesting that Δn_s induces strong changes in the free energy landscape of the system as a result of Coulomb interactions. The results from a third, waiting-time (t_w) protocol, where n_s is changed temporarily during t_w by a large amount, demonstrate that non-Gaussian PDFs exhibit history dependence and an evolution towards a Gaussian distribution as the system ages and slowly approaches equilibrium. By calculating the power spectra and higher-order statistics for the noise measured over a wide range of the applied voltage bias, it is established that the non-Gaussian noise is observed in the regime of Ohmic or linear response, i.e. that it is not caused by the applied bias.

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