Temperature-induced break up of strongly correlated electron state in InSb

We report the observation of a temperature-induced transition in highly com pensated n-InSb with la = 3 x 10(14) cm(-3) The temperature dependence of c onductivity shows the metal-like behavior (sigma proportional to T-1/2) at temperatures above the critical T-0 = 0.25 K. The transition was detected a s a crossover to the hopping transport at T < T-0. As we suppose. the therm al length L-T = (2 pi D (h) over bar/k(B) T)(1/2) rises With decreasing tem perature and reaches the correlation length determined by disorder (D is th e electron diffusion coefficient). At T < T-0, electrons become correlated, k(B)T(0) is approximately the Coulomb energy. In other words, thermal ener gy should be less than the energy of fluctuations considered by Anderson or Lifshits models. (C) 2000 Elsevier Science B.V. All rights reserved.