Mechanism of hopping transport in disordered Mott insulators

TL;DR

This paper uncovers a universal hopping transport mechanism in disordered Mott insulators near the metal-insulator transition, showing a systematic change in hopping exponent linked to disorder-induced localized states.

Contribution

It combines experimental data and theoretical analysis to reveal a novel, universal hopping mechanism in disordered Mott insulators close to the transition.

Findings

Hopping exponent evolves from 1/2 to 1/3 near the transition

Disorder-induced localized states emerge in the Mott-Hubbard gap

Universal behavior observed in disordered Mott systems

Abstract

By using a combination of detailed experimental studies and simple theoretical arguments, we identify a novel mechanism characterizing the hopping transport in the Mott insulating phase of Ca$_{2-x}$Sr$_x$RuO$_4$ near the metal-insulator transition. The hopping exponent $\alpha$ shows a systematic evolution from a value of $\alpha=1/2$ deeper in the insulator to the conventional Mott value $\alpha=1/3$ closer to the transition. This behavior, which we argue to be a universal feature of disordered Mott systems close to the metal-insulator transition, is shown to reflect the gradual emergence of disorder-induced localized electronic states populating the Mott-Hubbard gap.