Singular Effect of Disorder on Electronic Transport in Strong Coupling Electron-Phonon Systems

TL;DR

This study investigates how weak disorder dramatically affects electronic transport in strongly coupled electron-phonon systems, revealing enhanced resistivity, suppressed density of states, and altered temperature dependence.

Contribution

It provides a detailed analysis of disorder effects in the disordered Holstein model at strong coupling, highlighting the disorder-induced tendency towards polaron formation and transport anomalies.

Findings

Weak disorder greatly increases resistivity at zero temperature.

Disorder suppresses the density of states at the Fermi level.

Transport behavior shifts to insulating-like with decreasing temperature.

Abstract

We solve the disordered Holstein model in three dimensions considering the phonon variables to be classical. After mapping out the phases of the `clean' strong coupling problem, we focus on the effect of disorder at strong electron-phonon (EP) coupling. The presence of even weak disorder (i) enormously enhances the resistivity (\rho) at T=0, simultaneously suppressing the density of states at the Fermi level, (ii) suppresses the temperature dependent increase of \rho, and (iii) leads to a regime with d\rho/dT <0. We locate the origin of these anomalies in the disorder induced tendency towards polaron formation, and the associated suppression in effective carrier density and mobility. These results, explicitly at `metallic' density, are of direct relevance to disordered EP materials like covalent semiconductors, the manganites, and to anomalous transport in the A-15 compounds.