Self-organized defect strings in two-dimensional crystals

TL;DR

This study combines experiments and simulations to reveal how vacancies in 2D crystals form defect strings that propagate and interact, providing new insights into dislocation dynamics and topological defects in nano-materials.

Contribution

It demonstrates the formation and dynamics of defect strings in 2D crystals and measures dislocation interactions beyond spontaneous events, linking observations to elasticity theory.

Findings

Defect strings propagate via rapid gliding and rare rotations.

Dislocations at string ends have anti-parallel Burgers vectors.

Dislocation interactions follow a double-well potential explained by elasticity theory.

Abstract

Using experiments with single particle resolution and computer simulations we study the collective behaviour of multiple vacancies injected into two-dimensional crystals. We find that the defects assemble into linear strings that propagate through the crystal in a succession of rapid one-dimensional gliding phases and rare rotations, during which the direction of motion changes. At both ends, strings are terminated by dislocations with anti-parallel Burgers vectors. By monitoring the separation of the dislocations, we measure their effective interactions with high precision, for the first time beyond spontaneous formation and annihilation, and explain the double-well form of the dislocation interaction in terms of continuum elasticity theory. Our results give a detailed picture of the motion and interaction of dislocations in two dimensions and enhance our understanding of topological defects in two-dimensional nano-materials.