Universal scaling near band-tuned metal-insulator phase transitions

TL;DR

This paper develops a scaling theory for band-tuned metal-insulator transitions, explaining resistivity behavior and negative temperature coefficients observed in experiments, including Mooij correlations.

Contribution

It introduces a universal scaling framework for resistivity near band-tuned transitions, clarifying the origin of negative $dR/dT$ regimes and Mooij correlations.

Findings

Resistivity diverges as $1/T$ at the critical point.

Negative $dR/dT$ regimes can occur on the metallic side, mimicking insulators.

Mooij correlations are explained by the scaling theory with $T$-linear scattering.

Abstract

We present a theory for band-tuned metal-insulator transitions based on the Kubo formalism. Such a transition exhibits scaling of the resistivity curves, in the regime where $T\tau >1$ or $\mu \tau>1$, where $\tau$ is the scattering time and $\mu$ the chemical potential. At the critical value of the chemical potential, the resistivity diverges as a power law, $R_c \sim 1/T$. Consequently, on the metallic side there is a regime with negative $dR/dT$, which is often misinterpreted as insulating. We show that scaling and this `fake insulator' regime is observed in a wide range of experimental systems. In particular, we show that Mooij correlations in high-temperature metals with negative $dR/dT$ can be quantitatively understood with our scaling theory in the presence of $T$-linear scattering.