By carefully analyzing the low temperature density dependence of 2D conductivity in undoped high mobility n-GaAs heterostructures, we conclude that the 2D metal-insulator transition in this system is a density inhomogeneity driven percolation transition due to the breakdown of screening in the random charged impurity disorder background. In particular, our measured conductivity exponent of ∼1.4 approaches the 2D percolation exponent value of 4/3 at low temperatures and our experimental data are inconsistent with there being a zero-temperature quantum critical point in our system.
@article{arxiv.cond-mat/0406655,
title = {2D Metal-Insulator transition as a percolation transition},
author = {S. Das Sarma and M. P. Lilly and E. H. Hwang and L. N. Pfeiffer and K. W. West and J. L. Reno},
journal= {arXiv preprint arXiv:cond-mat/0406655},
year = {2009}
}