Activity induced isotropic-polar transition in active liquid crystals

TL;DR

This paper demonstrates a transition from an isotropic to a polar flowing state in active liquid crystals driven solely by active energy injection, highlighting the role of elastic absorption in the dynamics.

Contribution

It introduces an analytical framework and lattice Boltzmann simulations showing a novel active-induced phase transition without free-energy bias.

Findings

Observation of large fluctuations at the transition point

Elastic absorption significantly influences system dynamics

Transition driven purely by active energy injection

Abstract

Active fluids are intrinsically out-of-equilibrium systems due to the internal energy injection of the active constituents. We show here that a transition from a motion-less isotropic state towards a flowing polar one can be possibly driven by the sole active injection through the action of polar-hydrodynamic interactions in absence of an ad hoc free-energy which favors the development of an ordered phase. In particular, we propose an analytical argument and we perform lattice Boltzmann simulations where the appearance of large temporal fluctuations in the polar fraction of the system is observed at the transition point. Moreover, we make use of a scale-to-scale analysis to unveil the energy transfer mechanism, proving that elastic absorption plays a relevant role in the overall dynamics of the system, contrary to what reported in previous works on the usual active gel theory where this term could be factually neglected.