Surface Fluctuations and the Stability of Metal Nanowires

TL;DR

This paper models the surface fluctuations of metal nanowires, revealing how surface tension and quantum effects influence their stability and dynamics, including critical fluctuations and reentrant behavior at high temperatures.

Contribution

It introduces a continuum model that combines surface tension and electron-shell effects to analyze nanowire stability and surface dynamics, including nonlinear behavior.

Findings

Stability diagram shows stability fingers extending to high temperatures for certain conductance values.

Critical fluctuations occur at the stability boundary, leading to inhomogeneous nanowires.

Some unstable nanowires neck down to a smaller stable radius instead of breaking.

Abstract

The surface dynamics and thermodynamics of metal nanowires are investigated in a continuum model. Competition between surface tension and electron-shell effects leads to a rich stability diagram, with fingers of stability extending to extremely high temperatures for certain magic conductance values. The linearized dynamics of the nanowire's surface are investigated, including both acoustic surface phonons and surface self-diffusion of atoms. On the stability boundary, the surface exhibits critical fluctuations, and the nanowire becomes inhomogeneous. Some stability fingers coalesce at higher temperatures, or exhibit overhangs, leading to reentrant behavior. The nonlinear surface dynamics of unstable nanowires are also investigated in a single-mode approximation. We find evidence that some unstable nanowires do not break, but rather neck down to the next stable radius.