# Orientational ordering of closely packed Janus particles

## TL;DR

This study uses Monte Carlo simulations to explore how Janus particles in 2D pack and order, revealing a phase transition to stripe patterns with universality similar to the 3-state Potts model, and analyzing the dynamics of domain growth.

## Contribution

It demonstrates a phase transition in 2D Janus particles from disordered to stripe-ordered phases and identifies its universality class, providing insights into their orientational ordering.

## Key findings

- Disordered plastic crystal phase at small patch sizes.
- Stripe phase with broken three-fold symmetry at larger patches.
- Second-order phase transition with 3-state Potts universality.

## Abstract

We study orientational ordering of $2$-dimensional closely packed Janus particles by extensive Monte Carlo simulations. For smaller patch sizes the system remains in the plastic crystal phase where the rotational degrees of freedom are disordered down to the lowest temperatures. There the liquid consist of dimers and trimers of the attractive patches. For large enough patch sizes, the system exhibits a thermodynamic transition into a phase with stripe patterns of the patches breaking the three-fold rotational symmetry. Our results strongly suggests that the latter is a 2nd order phase transition whose universality is the same as that of the $3$-state Potts model in $2$-dimensions. Furthermore we analyzed the relaxation dynamics of the system performing quenching simulations into the stripe phase. We found growing domains of the stripes. The relaxation of key dynamical quantities follow universal scaling features in terms of the domain size.