Speaker
Description
The study of the formation of condensed, self-ordered phases has remained a central focus in the fields of condensed matter physics and particle physics over the past few decades. Examples of systems capable of forming ordered phases under confinement include electrons on the surface of liquid helium, electrons in quantum dots, and charged particles suspended in plasma1,2. A common characteristic among these systems is that they consist of particles with long-range repulsive interactions, typically confined by either parabolic or hard-wall potentials. Under such conditions, a typical structural arrangement is the Wigner crystal, which in two dimensions corresponds to a perfectly ordered triangular lattice. Systems forming 2D Wigner crystals under circular confinement—whether parabolic or hard-wall—have been identified as simplified models of 2D Thomson atoms3, exhibiting characteristic shell-like arrangements. However, such systems often rely on complex experimental architectures and demand sophisticated analysis techniques. Here, we propose a novel mesoscopic model based on solitary waves that can replicate the properties of condensed, self-ordered phases. Specifically, in a strongly confined nematic chiral liquid crystal. metastable toron-like structures can be generated in the form of solitary waves. These behave similarly to solid colloidal particles, with the unique feature that they are not physical entities with mass, but rather localised perturbations in the orientational order of the liquid crystal medium. The combination of elastic interactions arising from these local perturbations, the ability to control packing density, and the capacity to generate laterally confining structures within the liquid crystal leads to the emergence of highly ordered configurations reminiscent of 2D Wigner-like assemblies. Furthermore, when subjected to strong external perturbations—such as the application of lateral pressure—these torons can be annihilated, resulting in a malleable confined system. In this work, we investigate the behaviour of torons confined within a circular trap generated using holographic optical tweezers. We explore the dynamics of these solitonic structures under radial compression and demonstrate the existence of specific “magic numbers” corresponding to particularly stable configurations that exhibit shell-like ordering. We also show the stabilising capacity that the application of an electric field can have towards compression. Furthermore, we uncover the mechanism underlying the annihilation process that occurs under compression, highlighting its strong correlation with the coordination number of the solitons.
