Broken living layers: dislocations in active smectics

TL;DR

This paper demonstrates that in active 2D smectics with rotational symmetry, dislocations are always unbound due to noise, preventing a stable active smectic phase unless symmetry-breaking fields are applied, which still offer less stability than equilibrium counterparts.

Contribution

It reveals the fundamental instability of active 2D smectics caused by noise and analyzes how symmetry-breaking fields influence their stability.

Findings

Dislocations are always unbound in active 2D smectics with noise.

Active smectics are less stable than equilibrium smectics under weak symmetry-breaking fields.

Applying symmetry-breaking fields can stabilize active smectics, but stability remains limited.

Abstract

We show that dislocations in active 2d smectics with underlying rotational symmetry are always unbound in the presence of noise, meaning the active smectic phase does not exist for non-zero noise in $d=2$. The active smectic phase can, like equilibrium smectics in 2d, be stabilized by applying rotational symmetry breaking fields; however, even in the presence of such fields, active smectics are still much less stable against noise than equilibrium ones, when the symmetry breaking field(s) are weak.