Kondo-like behavior near the metal-to-insulator transition of nano-scale granular aluminum

TL;DR

This paper demonstrates that nano-scale granular aluminum films near the metal-insulator transition exhibit Kondo-like behaviors, including negative magnetoresistance and resistance minima, linked to spin-flip scattering at interfaces, coexisting with enhanced superconductivity.

Contribution

It reveals Kondo-like transport phenomena in granular aluminum films and attributes these to spin-flip scattering at metal/oxide interfaces, expanding understanding of electron interactions in such systems.

Findings

Observation of negative magnetoresistance

Resistance minimum at temperature Tm

Logarithmic resistance increase at low temperatures

Abstract

We show that the normal state transport properties of nano-scale granular Aluminum films, near the metal to insulator transition, present striking similarities with those of Kondo systems. Those include a negative magneto-resistance, a minimum of resistance R at a temperature Tm in metallic films, a logarithmic rise at low temperatures and a negative curvature of R(T) at high temperatures. These normal state properties are interpreted in terms of spin-flip scattering of conduction electrons by local magnetic moments, possibly located at the metal/oxide interfaces. Their co-existence with the enhanced superconductivity seen in these films is discussed.