Force, charge, and conductance of an ideal metallic nanowire

TL;DR

This paper models the mechanical and electrical properties of ideal metallic nanowires, revealing oscillations in force and conductance during stretching, and highlighting the importance of mesoscopic effects and charge fluctuations.

Contribution

It provides an exact quantum-mechanical analysis of nanowire properties, including force, conductance, and charge, using scattering matrix formalism and compares with adiabatic approximations.

Findings

Oscillations in tensile force during stretching.

Quantized jumps in conductance correlated with force oscillations.

Prediction of mesoscopic charge fluctuations of order e.

Abstract

The conducting and mechanical properties of a metallic nanowire formed at the junction between two macroscopic metallic electrodes are investigated. Both two- and three-dimensional wires with a W(ide)-N(arrow)-W(ide) geometry are modelled in the free-electron approximation with hard-wall boundary conditions. Tunneling and quantum-size effects are treated exactly using the scattering matrix formalism. Oscillations of order E_F/lambda_F in the tensile force are found when the wire is stretched to the breaking point, which are synchronized with quantized jumps in the conductance. The force and conductance are shown to be essentially independent of the width of the wide sections (electrodes). The exact results are compared with an adiabatic approximation; the later is found to overestimate the effects of tunneling, but still gives qualitatively reasonable results for nanowires of length L>>lambda_F, even for this abrupt geometry. In addition to the force and conductance, the net charge of the nanowire is calculated and the effects of screening are included within linear response theory. Mesoscopic charge fluctuations of order e are predicted which are strongly correlated with the mesoscopic force fluctuations. The local density of states at the Fermi energy exhibits nontrivial behavior which is correlated with fine structure in the force and conductance, showing the importance of treating the whole wire as a mesoscopic system rather than treating only the narrow part.