Comment on "Nonlinear current-voltage curves of gold quantum point contacts" [Appl. Phys. Lett. 87, 103104 (2005)]

TL;DR

This paper critiques a previous explanation for nonlinear IV curves in gold quantum point contacts, proposing that electron shell effects, rather than thermal expansion, are responsible for the observed phenomena.

Contribution

It introduces the role of electron shell effects in preventing wire thickening in long gold quantum point contacts, challenging prior thermal expansion explanations.

Findings

Electron shell effects favor certain wire radii.

Long wires do not thicken under compression due to shell effects.

Short wires are more affected by thermal expansion.

Abstract

In a recent Letter [Appl. Phys. Lett. 87, 103104 (2005)], Yoshida et al. report that nonlinearities in current-voltage curves of gold quantum point contacts occur as a result of a shortening of the distance between electrodes at finite bias, presumably due to thermal expansion. For short wires, the electrode displacement induces a thickening of the wire, as well as nonlinearities of the IV curve, while the radius of long wires is left unchanged, thus resulting in a linear IV curve. We argue here that electron shell effects, which favor wires with certain "magic radii," prevent the thickening of long wires under compression, but have little effect on wires below a critical length.