Publication Office of Progress of Theoretical Physics, Progress of Theoretical Physics -- Supplement-, (166), p. 136-142
DOI: 10.1143/ptps.166.136
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For a system of localised electron states the DC conductivity vanishes at zero temperature, but localised electrons can conduct at finite temperature. Mott gave a theory for the low-temperature conductivity in terms of a variable-range hopping model, which is hard to analyse. Here we give precise asymptotic results for a modified variable-range hopping model, proposed by S. Alexander [Phys. Rev. B, 26, 2956 (1982)]. If a system has localised electron states the DC conductivity must be zero at zero temperature, but localised electrons can conduct at finite temperatures. Mott 1) proposed that the low-temperature dependence of the DC conductivity is