Length matters: keeping atomic wires in check

TL;DR

This paper investigates how non-conservative forces affect atomic wires during current flow, showing that phonon modes and system length influence stability, with static calculations predicting dynamic effects.

Contribution

It introduces a static calculation approach to predict non-conservative effects in atomic wires, aiding the design of stable nanoscale conductors.

Findings

Kinetic energy concentrates in few phonon modes during initial transient

Static calculations can predict non-conservative effects before real-time simulations

Ion kinetic energy decreases with system length and increases with atomic mass

Abstract

Dynamical effects of non-conservative forces in long, defect free atomic wires are investigated. Current flow through these wires is simulated and we find that during the initial transient, the kinetic energies of the ions are contained in a small number of phonon modes, closely clustered in frequency. These phonon modes correspond to the waterwheel modes determined from preliminary static calculations. The static calculations allow one to predict the appearance of non-conservative effects in advance of the more expensive real-time simulations. The ion kinetic energy redistributes across the band as non-conservative forces reach a steady state with electronic frictional forces. The typical ion kinetic energy is found to decrease with system length, increase with atomic mass, and its dependence on bias, mass and length is supported with a pen and paper model. This paper highlights the importance of non-conservative forces in current carrying devices and provides criteria for the design of stable atomic wires.