Constancy of Minimum Metallic Conductivity in Two Dimensions

A scaling argument is used to demonstrate the existence of a minimum metallic conductivity with a universal value for two-dimensional random lattices. We present a summary of the results of a detailed numerical experiment which supports this suggestion and indicates that the minimum metallic conductivity is $(0.12\ifmmode\pm\else\textpm\fi{}0.03)\frac{{e}^{2}}{\ensuremath{\hbar}}$, in fair agreement with some experimental results for inversion layers.