Hall effect at a tunable metal-insulator transition

Abstract

Using a rotating magnetic field, the Hall effect in three-dimensional amorphous ${\mathrm{Gd}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}$ has been measured in the critical regime of the metal-insulator transition for a constant total magnetic field. The Hall coefficient ${R}_{0}$ is negative, indicating electronlike conductivity, with a magnitude that increases with decreasing conductivity. ${R}_{0}$ diverges at the metal-insulator transition, and displays critical behavior with exponent $\ensuremath{-}1$ $[{R}_{0}\ensuremath{\sim}(H\ensuremath{-}{H}_{C}{)}^{\ensuremath{-}1}].$ This dependence is interpreted as a linear decrease in the density of mobile carriers $n\ensuremath{\sim}{R}_{0}^{\ensuremath{-}1}\ensuremath{\sim}H\ensuremath{-}{H}_{C},$ indicative of the dominant influence of interaction effects.