Spin-polarized transport in copper-oxide atomic junctions revealed by anomalous shot-noise behavior in presence of the Kondo effect

Abstract

Noise measurements provide a valuable tool for revealing spin polarization effects in the electronic transport through quantum coherent conductors. We present an extension of the Landauer description of shot noise to include energy-dependent transmission functions and apply it to explore local magnetic correlations in air-oxidized copper contacts, for which first-principle studies have predicted the emergence of ferromagnetic ground states, attributing certain atomic configurations with spin filtering capabilities. By means of low-temperature transport measurements, we provide comprehensive experimental evidence, including hysteretic magnetoresistance and zero-bias anomalies (ZBAs) attributed to the Kondo effect, for the presence of local magnetism. The analysis of the anomalous shot noise in the presence of ZBAs allows us to determine the spin polarization of the current which may reach even full polarization, confirming the spin-filtering capability of copper oxide atomic contacts.