Sharp Metal-Insulator Transition in a Random Solid

Abstract

Zero-temperature metallic conductivities have been measured above and below Mott's minimum value ${\ensuremath{\sigma}}_{min}$ in bulk crystals of P-doped Si. Conductivities below ${\ensuremath{\sigma}}_{min}$ increase by over ${10}^{3}$ as the density is raised by less than 1%, and do not rule out a discontinuous transition. However, over a wider density range the data can be fitted with a scaling form with a characteristic length that tends to diverge with the same exponent in the metal and insulator.