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

S. Das Sarma, E. H. Hwang, and Qiuzi Li
Phys. Rev. B 88, 155310 – Published 10 October 2013

Abstract

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 two-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 two-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. The calculated density- and temperature-dependent resistivity in our theory mimics the phenomenology of 2D MIT experiments with reasonable parameter values for the background disorder.

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  • Received 11 June 2013

DOI:https://doi.org/10.1103/PhysRevB.88.155310

©2013 American Physical Society

Authors & Affiliations

S. Das Sarma1, E. H. Hwang1,2, and Qiuzi Li1

  • 1Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
  • 2SKKU Advanced Institute of Nanotechnology and Department of Physics, Sungkyunkwan University, Suwon 440-746, Korea

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Vol. 88, Iss. 15 — 15 October 2013

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