Direct imaging of thermally excited metastable structures of ion Coulomb clusters

TL;DR

This paper presents the direct imaging of thermally excited metastable structures in large ion Coulomb clusters, revealing structural excitations caused by finite temperatures in a system of thousands of laser-cooled ions.

Contribution

It provides the first direct observation of thermally induced metastable structures in large Coulomb ion clusters, advancing understanding of finite-temperature effects in such systems.

Findings

Direct imaging of metastable structures in ion clusters

Identification of thermal excitations in Coulomb crystals

Observation of temperature-induced structural dynamics

Abstract

Coulomb crystallisation of large ensembles of ions has in the past years been intensively studied experimentally with many spectacular results of relevance to infinite systems in one-, two-, and three-dimensions.While strings of a few ions have proven to be very attractive objects in quantum information processing, larger Coulomb crystals have very recently found applications within other aspects the dynamics of quantum systems. Smaller finite ensembles of cold identical charged particles confined by a harmonic potential furthermore constitute very special types of clusters due to the pure repulsive long-range inter-particle forces. Here, we report on the direct imaging of metastable structures of Coulomb clusters consisting of a few thousands confined and laser-cooled 40Ca+ ions. The observations are attributed to structural excitations due to finite temperatures, a feature likely to appear in clusters of short-range interacting particles, but yet not observed directly.