Chain-like transitions in Wigner crystals: Sequential or non-sequential?

TL;DR

This study investigates the structural phase transitions of Wigner crystals in quasi-one-dimensional channels, revealing conditions favoring sequential or non-sequential chain configurations and highlighting the impact of interaction range, confinement, and disorder.

Contribution

It demonstrates that long-range interactions and hard-wall confinement favor sequential transitions, and shows how disorder suppresses non-sequential transitions, explaining their experimental absence.

Findings

Sequential transitions are favored by long-range interactions and hard-wall confinement.

Small structural disorder suppresses non-sequential transitions.

Energy barriers influence the preferred transition pathway.

Abstract

The structural transitions of the ground state of a system of repulsively interacting particles confined in a quasi-one-dimensional channel, and the effect of the interparticle interaction as well as the functional form of the confinement potential on those transitions are investigated. Although the non-sequential ordering of transitions (non-SOT), i.e. $1$-$2$-$4$-$3$-$4$-$5$-$6$-$...$ sequence of chain configurations with increasing density, is widely robust as predicted in a number of theoretical studies, the sequential ordering of transitions (SOT), i.e.~$1$-$2$-$3$-$4$-$5$-$6$-$...$ chain, is found as the ground state for long-ranged interparticle interaction and hard-wall-like confinement potentials. We found an energy barrier between every two different phases around its transition point, which plays an important role in the preference of the system to follow either a SOT or a non-SOT. However, that preferential transition requires also the stability of the phases during the transition. Additionally, we analyze the effect of a small structural disorder on the transition between the two phases around its transition point. Our results show that a small deformation of the triangular structure, change dramatically the picture of the transition between two phases, removing in a considerable region the non-SOT in the system. This feature could explain the fact that the non-SOT is, up to now, not observed in experimental systems, and suggests a more advanced experimental set-up to detect the non-SOT.