# Generic first-order phase transitions between isotropic and orientational phases with polyhedral symmetries

## TL;DR

This paper uses a non-Abelian gauge theory and Monte Carlo simulations to show that all three-dimensional polyhedral nematic to isotropic phase transitions are generally first-order, providing a universal understanding of these exotic symmetry-breaking transitions.

## Contribution

It introduces a gauge theory approach to classify and analyze phase transitions in polyhedral nematics with complex symmetries, extending beyond traditional methods.

## Key findings

- All polyhedral nematic-isotropic transitions are first-order.
- The results align with renormalization group predictions.
- Second-order transitions require fine-tuning.

## Abstract

Polyhedral nematics are examples of exotic orientational phases that possess a complex internal symmetry, representing highly non-trivial ways of rotational symmetry breaking, and are subject to current experimental pursuits in colloidal and molecular systems. The classification of these phases has been known for a long time, however, their transitions to the disordered isotropic liquid phase remain largely unexplored, except for a few symmetries. In this work, we utilize a recently introduced non-Abelian gauge theory to explore the nature of the underlying nematic-isotropic transition for all three-dimensional polyhedral nematics. The gauge theory can readily be applied to nematic phases with an arbitrary point-group symmetry, including those where traditional Landau methods and the associated lattice models may become too involved to implement owing to a prohibitive order-parameter tensor of high rank or (the absence of) mirror symmetries. By means of exhaustive Monte Carlo simulations, we find that the nematic-isotropic transition is generically first-order for all polyhedral symmetries. Moreover, we show that this universal result is fully consistent with our expectation from a renormalization group approach, as well as with other lattice models for symmetries already studied in the literature. We argue that extreme fine tuning is required to promote those transitions to second order ones. We also comment on the nature of phase transitions breaking the $O(3)$ symmetry in general cases.