Universality of the close packing properties and markers of isotropic-to-tetratic crossover in quasi-one-dimensional superdisk fluid

TL;DR

This study investigates the ordering and packing properties of quasi-one-dimensional superdisk fluids, revealing a universal transition from isotropic to tetratic phases and shape-independent relations in close packing behaviour.

Contribution

It introduces a comprehensive analysis of phase transition and close packing in anisotropic superdisk systems constrained to one dimension, highlighting universal relations.

Findings

Transition from isotropic to tetratic regime with increasing density

Larger, more anisotropic particles are denser in the tetratic phase

Universal, shape-independent relations between pressure, angular fluctuations, and correlation length

Abstract

We study equilibrium states and ordering regimes of a quasi-one-dimensional system of hard superdisks (anisotropic particles interpolating between disks and squares) where the centers of the particles are constrained to move on a line. A continuous change from a quasi-isotropic to a tetratic regime is found upon increasing the density. Somewhat unexpected, for isobaric states, systems with larger and more anisotropic particles in the tetratic regime are denser than systems with smaller and less anisotropic particles in a quasi-isotropic regime. Close packing behaviour is characterised by exponents describing the behaviour of the pressure, the angular fluctuations and the angular correlation length. We obtain two universal, shape-independent relations between them.