# Defects in vertically vibrated monolayers of cylinders

## TL;DR

This study investigates defect formation and liquid-crystalline ordering in vibrated monolayers of cylinders, revealing tetratic arrangements with boundary-induced defects and proposing a new method to measure elastic properties.

## Contribution

It demonstrates the formation of tetratic order and boundary defects in vibrated cylinders, and introduces a novel approach to measure elastic properties in such non-equilibrium systems.

## Key findings

- Tetratic arrangements with four point defects are observed.
- Monte Carlo simulations confirm experimental results.
- A new method to measure elastic properties in vibrated systems is developed.

## Abstract

We analyse liquid-crystalline ordering in vertically vibrated monolayers of cylinders confined in a circular cavity. Short cylinders form tetratic arrangements with C$_4$ symmetry. This symmetry, which is incompatible with the geometry of the cavity, is restored by the presence of four point defects with total topological charge $+4$. Equilibrium Monte Carlo simulations predict the same structure. A new method to measure the elastic properties of the tetratic medium is developed which exploits the clear similarities between the vibrated dissipative system and the thermal equilibrium system. Our observations open up a new avenue to investigate the formation of defects in response to boundary conditions, an issue which is very difficult to realize in colloidal or molecular systems.