First order alignment transition in an interfaced active nematic

TL;DR

This study demonstrates a first order phase transition in an active nematic layer interfaced with a passive liquid crystal, showing abrupt changes in flow and orientation under temperature and magnetic field variations.

Contribution

It provides experimental evidence of a first order transition in an active nematic system coupled with a passive liquid crystal, highlighting the role of external stimuli.

Findings

Active nematic reorganization from turbulence to laminar flow under phase transition.

Intermittent dynamics and coexistence of different phases observed.

Transition characterized as discontinuous, unlike the passive fluid's continuous transition.

Abstract

We investigate experimentally the dynamic phase transition of a two-dimensional active nematic layer interfaced with a passive liquid crystal. Under a temperature ramp that leads to the transition of the passive liquid into a highly anisotropic lamellar smectic-A phase, and in the presence of a magnetic field, the coupled active nematic reorganizes its flow and orientational patterns from the turbulent into a quasi-laminar regime aligned perpendicularly to the field. Remarkably, while the phase transition of the passive fluid is known to be continuous, our observations reveal intermittent dynamics of the order parameter and the coexistence of aligned and turbulent regions in the active nematic, a signature of discontinuous, or first order, phase transitions.