Impurities and Defects in Mott Systems

TL;DR

This paper explores how strong electronic correlations near a Mott insulator suppress impurity scattering in cuprates and reveals a shock wave mechanism in resistive switching devices, linking fundamental physics with practical applications.

Contribution

It provides a theoretical framework explaining impurity robustness in cuprates and introduces a shock wave model for oxygen vacancy migration in resistive switching systems.

Findings

Correlation effects suppress impurity scattering rates.

Forward scattering amplitude is enhanced by correlations.

Oxygen vacancy migration can form shock waves affecting device switching.

Abstract

Disorder has intriguing consequences for correlated electronic materials, which include several families of high-temperature superconductors and resistive switching systems. We address the question of why strongly correlated d-wave superconductors, such as the cuprates, prove to be surprisingly robust against the introduction of non-magnetic impurities. We show that, very generally, both the pair-breaking and the normal state transport scattering rates are significantly suppressed by strong correlations effects arising in the proximity to a Mott insulating state. We also show that the correlation-renormalized scattering amplitude is generically enhanced in the forward direction, an effect which was previously often ascribed to the specific scattering by charged impurities outside the copper-oxide planes. We provide the theoretical insights for resistive switching systems and show how impurities and underlying correlations can play significant roles in practical devices. We report the striking result of a connection between the resistive switching and shock wave formation, a classic topic of non-linear dynamics. We argue that the profile of oxygen vacancies that migrate during the commutation forms a shock wave that propagates through a highly resistive region of the device. We validate the scenario by means of model simulations and experiments in a manganese-oxide based memristor device and we extend our theory to the case of binary oxides. The shock wave scenario brings unprecedented physical insight and enables to rationalize the process of oxygen-vacancy-driven resistive change with direct implications for a key technological aspect- the commutation speed.