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Preexponential factor in variable-range hopping conduction in CuInTe <inf>2</inf>

Abstract:

We study the temperature dependence of the electrical resistivity in a single crystal of p-type uncompensated CuInTe2 on the insulating side of the metal-insulator transition down to 0.4 K. We observe a crossover from Mott to Efros-Shklovskii variable-range hopping conduction. In Efros-Shklovskii-type conduction, the resistivity is best described by explicitly including a preexponential temperature dependence according to the general expression ρ=ρ0Tαexp(T ES/T)1/2, with α≠0. A theory based on the resistor network model was developed to derive an explicit relation between α and the decay of the wavefunction of the localized states. A consistent correspondence between the asymptotic extension of the wavefunction and the conduction regime is proposed. The results indicate a new mechanism for a local resistivity maximum in insulators, not involving magnetic effects. © 2005 Elsevier Ltd. All rights reserved.