# Diversity of knot solitons in liquid crystals manifested by linking of preimages in torons and hopfions

## TL;DR

This paper demonstrates the experimental and numerical discovery of diverse, knotted topological solitons in liquid crystals, revealing complex structures and topologies previously unobserved in theory and experiments.

## Contribution

It introduces a novel method to analyze topological solitons in liquid crystals, uncovering a wide variety of knotted structures and exploring their topological properties and formation conditions.

## Key findings

- Discovered a large diversity of knotted solitons in liquid crystals.
- Linked the topology of solitons to medium properties like chirality and elasticity.
- Showed static 3D solitons can exist without additional defects.

## Abstract

Topological solitons are knots in continuous physical fields classified by non-zero Hopf index values. Despite arising in theories that span many branches of physics, from elementary particles to condensed matter and cosmology, they remain experimentally elusive and poorly understood. We introduce a method of experimental and numerical analysis of such localized structures in liquid crystals that, similar to the mathematical Hopf maps, relates all points of the medium's order parameter space to their closed-loop preimages within the three-dimensional solitons. We uncover a surprisingly large diversity of naturally occurring and laser-generated topologically nontrivial solitons with differently knotted nematic fields, which previously have not been realized in theories and experiments alike. We discuss the implications of the liquid crystal's non-polar nature on the knot soliton topology and how the medium's chirality, confinement and elastic anisotropy help to overcome the constrains of the Hobart-Derrick theorem, yielding static three-dimensional solitons without or with additional defects. Our findings will establish chiral nematics as a model system for experimental exploration of topological solitons and may impinge on understanding of such nonsingular field configurations in other branches of physics, as well as may lead to technological applications