Statistics of quantum transport in metal nanowires with surface disorder

TL;DR

This paper models quantum transport in sodium nanowires with surface disorder, explaining conductance histogram peaks and shot noise behavior through a modified free-electron approach, bridging experimental observations at high conductance levels.

Contribution

It introduces a modified disordered free-electron model that explains high conductance peaks and shot noise saturation in metallic nanowires, extending previous models to higher conductance regimes.

Findings

Conductance peaks at high values are due to combined quantized conductance peaks.

The model explains the interplay of disorder and quantization in conductance histograms.

Shot noise saturates at about 1/10 of the classical value at high conductance.

Abstract

Experimental conductance histograms built from several thousand successive breakings of sodium nanowires exhibit peaks up to rather high conductance values (100 x 2e^2/h). In this paper, we present results from a disordered free-electron model of a metallic nanowire, which was previously successful in describing both conductance histograms and shot noise measurements in gold nanocontacts with much lower conductances. We find in particular that, with a modification of the model of disorder, the conductance histogram can be understood as an interplay of conductance quantization and disorder for low conductances (G < 10 x 2e^2/h), while peaks corresponding to higher conductance are actually a combination of several ``quantized conductance peaks''. We also predict a saturation of the shot noise at high conductance to about 1/10 of its classical value 2eI.