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arXiv 1306.2621cond-mat.mes-hall
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势涨落驱动的二维金属-绝缘体转变的半经典输运现象

Two-dimensional metal-insulator-transition as a potential fluctuation driven semiclassical transport phenomenon

S. Das Sarma, E. H. Hwang, Qiuzi Li

摘要:

我们理论上考虑的载流子密度调谐(表观)的二维(2D)金属-绝缘体-过渡(MIT)在半导体异质结为基础的2D载流子系统所产生的一个经典的渗流现象的不均匀密度景观所产生的随机淬火带电杂质的环境中的长程电位波动。半导体中固有的长程库仑无序在2D系统中产生强烈的电势波动,其中一部分载流子被捕获或经典局部化,导致在中等密度下的混合2组分半经典输运行为,其中一部分载流子是移动的,另一部分是固定的。在高载流子密度下,所有载流子基本上都是移动的,而在低载流子密度下,所有载流子基本上都被捕获,因为不可能存在通过湖泊和山脉不均匀的电势景观的移动传输路径。没有渗透的低密度情况将模仿绝缘体,而允许通过湖泊和山脉能量景观的路径的高密度情况将模仿金属,系统在两者之间表现出明显的MIT。我们计算的载流子密度,杂质密度,杂质的位置,和温度的函数的输运特性,使用2-组分(捕获和移动载流子)有效介质理论。我们的理论计算的输运性质与实验观察到的二维电子和空穴系统中的二维MIT现象有很好的定性一致性。我们发现一个高(低)密度金属(绝缘)的温度依赖性的二维电阻率,和一个中等密度的交叉行为,可以确定与实验观察到的二维MIT。

英文摘要:

We theoretically consider the carrier density tuned (apparent) two-dimensional (2D) metal-insulator-transition (MIT) in semiconductor heterostructure-based 2D carrier systems as arising from a classical percolation phenomenon in the inhomogeneous density landscape created by the long-range potential fluctuations induced by random quenched charged impurities in the environment. The long-range Coulomb disorder inherent in semiconductors produces strong potential fluctuations in the 2D system where a fraction of the carriers gets trapped or classically localized, leading to a mixed 2-component semiclassical transport behavior at intermediate densities where a fraction of the carriers is mobile and another fraction immobile. At high carrier density, all the carriers are essentially mobile whereas at low carrier density all the carriers are essentially trapped since there is no possible percolating transport path through the lake-and-mountain inhomogeneous potential landscape. The low-density situation with no percolation would mimic an insulator whereas the high-density situation with allowed percolating paths through the lake-and-mountain energy landscape would mimic a metal with the system manifesting an apparent MIT in between. We calculate the transport properties as a function of carrier density, impurity density, impurity location, and temperature using a 2-component (trapped and mobile carriers) effective medium theory. Our theoretically calculated transport properties are in good qualitative agreement with the experimentally observed 2D MIT phenomenology in 2D electron and hole systems. We find a high (low) density metallic (insulating) temperature-dependence of the 2D resistivity, and an intermediate-density crossover behavior which could be identified with the experimentally observed 2D MIT.

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