The smallest length scale near the metal-insulator transition

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Abstract
It is shown that very near the metal-insulator transition in a three-dimensional system at very low temperatures (T), the inelastic diffusion length (Li) is reduced and may become the smallest length scale. In this region the conductivity, sigma , follows the law sigma = sigma 0+mT1/2 where the T1/2 dependence arises primarily from a diffusion length Li approximately sigma 032//T1/2 which is smaller than the interaction length LT approximately sigma 12//T1/2 when sigma 0 is small. The authors present experimental evidence for these results. In particular, for InSb they find m varies as sigma 0-3/2 and for compensated GaAs they find negative magnetoresistance near the transition, which yields Li approximately T-1/2.