Velocity plateaus and jumps in carbon nanotube sliding

TL;DR

This study uses molecular dynamics simulations to reveal that the sliding velocity of concentric carbon nanotubes exhibits jumps and plateaus driven by friction peaks, challenging the expectation of smooth velocity increase under external force.

Contribution

It introduces a novel analysis of nanotube sliding dynamics under external force, highlighting velocity jumps and plateaus caused by friction peaks, which was not previously observed.

Findings

Velocity exhibits jumps and plateaus with increasing force.

Friction peaks cause stable and unstable velocity branches.

Phenomena resemble conduction and breakdown in ionized gases.

Abstract

The friction between concentric carbon nanotubes sliding one inside the other has been widely studied and simulated, but not so far using external force as the driving variable. Our molecular dynamics (MD) simulations show that as the pulling force grows, the sliding velocity increases by jumps and plateaus rather than continuously as expected. Dramatic friction peaks (similar to that recently noted by Tangney {\it et al.} in Phys. Rev. Lett. 97 (2006) 195901) which develop around some preferential sliding velocities, are at the origin of this phenomenon. The (stable) rising edge of the peak produces a velocity plateau; the (unstable) dropping edge produces a jump to the nearest stable branch. The outcome is reminiscent of conduction in ionized gases, the plateau correspon ding to a current stabilization against voltage variations, the jump corresponding to a discharge or breakdown.