Formation of helical ion chains

TL;DR

This paper investigates the nonequilibrium formation of helical ion chains during a phase transition in a trapped ion system, demonstrating how quench rates influence the winding number and confirming predictions of the Kibble-Zurek theory.

Contribution

It provides a detailed analysis of how controlled quench rates lead to helical structures in ion chains, linking experimental dynamics to theoretical scaling laws.

Findings

Winding number scales with quench rate as predicted by Kibble-Zurek theory.

Formation of helical ion chains depends on the trap topology and cooling.

Good quantitative agreement between simulations and theoretical predictions.

Abstract

We study the nonequilibrium dynamics of the linear to zigzag structural phase transition exhibited by an ion chain confined in a trap with periodic boundary conditions. The transition is driven by reducing the transverse confinement at a finite quench rate, which can be accurately controlled. This results in the formation of zigzag domains oriented along different transverse planes. The twists between different domains can be stabilized by the topology of the trap and under laser cooling the system has a chance to relax to a helical chain with nonzero winding number. Molecular dynamics simulations are used to obtain a large sample of possible trajectories for different quench rates. The scaling of the average winding number with different quench rates is compared to the prediction of the Kibble-Zurek theory, and a good quantitative agreement is found.