Theory of Electron Transport near Anderson-Mott Transitions

TL;DR

This paper develops a theory for electron transport near Anderson-Mott transitions, emphasizing the role of a soft Hubbard gap in the density of states and its impact on resistivity, supported by experimental comparisons.

Contribution

It introduces a novel soft Hubbard gap concept affecting the density of states and derives a critical behavior formula for resistivity near the transition.

Findings

Evidence for soft Hubbard gap from experimental data

Derived formula matches resistivity temperature dependence

Supports coexistence of randomness and interactions in insulators

Abstract

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. Anderson insulators, caused by randomness, are characterized by a nonzero DOS at the Fermi energy. However, recently, the authors proposed that coexisting randomness and short-ranged interaction in insulators open a soft Hubbard gap in the DOS, and the DOS vanishes only at the Fermi energy. 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 kappa-(BEDT-TTF)_2Cu[N(CN)_2]Br demonstrate the evidence for the present soft-Hubbard scaling.