Metal-insulator transition in amorphous Ga-Ar mixtures: Critical exponents of electrical transport parameters and behavior of superconductivity

The experimentally determined critical exponents ν and g of electrical dc conductivity σ and Hall coefficient ${\mathit{R}}_{\mathit{H}}$ approaching the metal-insulator transition (MIT) from the metallic side in amorphous ${\mathrm{Ga}}_{\mathit{x}}$ ${\mathrm{Ar}}_{1\mathrm{-}\mathit{x}}$ mixtures are ν=0.5±0.1 and g=0.03±0.05, respectively. These exponents are the same as those found in Si:P and Si:As. We thus conclude that the MIT in these systems belong to the same universality class. Furthermore, we find that the disappearance of superconductivity in these mixtures coincides with the MIT.