Length Scales at the Metal-Insulator Transition in Compensated GaAs

We present results on the magnetic-field-induced metal-insulator transition in compensated GaAs. The electrical conductivity was found to obey $\sigma =a+b{T}^{\frac{1}{3}}$ down to 60 mK, on both sides of the transition, where $a$ and $b$ were constant for a given magnetic field. This indicates that the conductivity is determined by the shortest length scale, in this case the interaction length, on both the metallic and insulating sides of the transition. Thus, the behavior of the conductivity is essentially unchanged as the transition is scanned, as long as one length scale dominates.