Two-temperature activity induces liquid-crystal phases inaccessible in equilibrium

TL;DR

This study demonstrates that two-temperature activity in soft spherocylinder systems induces liquid-crystal phases, such as nematic and smectic, which are not accessible in equilibrium conditions, revealing new phase behavior driven by activity.

Contribution

The paper introduces a novel two-temperature active system that exhibits liquid-crystal phases beyond equilibrium limits, expanding understanding of active matter phase behavior.

Findings

Nematic phase observed at L/D=3, below the equilibrium threshold.

Smectic phase observed at L/D=2, above the critical activity.

Activity induces phase separation and self-organization not seen in equilibrium.

Abstract

In equilibrium hard-rod fluids, and in effective hard-rod descriptions of anisotropic soft-particle systems, the transition from the isotropic (I) phase to the nematic phase (N) is observed above the rod aspect ratio L/D = 3.70 as predicted by Onsager. We examine the fate of this criterion in a molecular dynamics study of a system of soft repulsive spherocylinders rendered active by coupling half the particles to a heat bath at a higher temperature than that imposed on the other half. We show that the system phase separates and self-organizes into various liquid-crystalline phases that are not observed in equilibrium for the respective aspect ratios. In particular, we find a nematic phase for L/D = 3 and a smectic phase for L/D = 2 above a critical activity.