Efros-Shklovskii variable-range hopping

If it is assumed that a migrating electron suffers a Coulombic attraction with the hole remaining on the parent cation, then the Efros-Shklovskii variable-range hopping law is appropriate ... 

It is found that the Mott variable-range hopping law often holds at intermediate temperatures and the Efros-Shklovskii variable-range hopping law at lower temperatures. 

As the first insulating/semiconducting higher boride series, the electrical transport of these compounds has been carefully investigated (e.g. Slack et al., 1977 Golikova, 1987 Werheit et al., 1991). The temperature dependence of the resistivity p follows the dependency of Mott s variable range hopping (VRH) model for 3 dimensional systems (Mott, 1968 Efros and Shklovskii, 1985), where... 

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