We present a theory of the DC electron transport in insulators near Anderson-Mott transitions under the influence of coexisting electron correlation and randomness. At sufficiently low temperatures, the DC electron transport in Anderson-Mott insulators is determined by the single-particle density of states (DOS) near the Fermi energy (EF). Anderson insulators, caused by randomness, are characterized by a nonzero DOS at EF. However, recently, the authors proposed that coexisting randomness and shortranged interaction in insulators open a soft Hubbard gap in the DOS, and the DOS vanishes only at EF. Based on the picture of the soft Hubbard gap, we derive a formula for the critical behavior for the temperature dependence of the DC resistivity. Comparisons of the present theory with experimental results of electrostatic carrier doping into an organic conductor k-(BEDT-TTF) 2Cu[N(CN)2]Br demonstrate the evidence for the present soft-Hubbard scaling.
ASJC Scopus subject areas