Active smectics on a sphere.

Area of Science:

• Soft Matter Physics
• Active Matter Physics
• Liquid Crystal Dynamics

Background:

• Understanding the behavior of active matter, particularly liquid crystals, is crucial for developing new materials and technologies.
• Confining active matter to curved surfaces introduces complex topological and geometrical constraints that influence its dynamics.
• Topological defects play a key role in the self-organization and emergent behavior of active systems.

Purpose of the Study:

• To investigate the dynamics of active smectic liquid crystals on a spherical surface.
• To analyze the formation, annihilation, and coarsening of topological defects in this confined active system.
• To identify characteristic defects and understand their role in determining the steady-state configurations.

Main Methods:

• Utilizing an active phase field crystal model to simulate the system's behavior.
• Initiating simulations from a randomly perturbed isotropic phase to observe spontaneous defect formation.
• Analyzing defect densities over time to identify scaling laws and dynamical exponents.

Main Results:

• Spontaneous formation and subsequent annihilation of topological defects during a coarsening process.
• Identification of complex scaling laws for defect densities with distinct dynamical exponents.
• Observation of accelerated coarsening on a sphere compared to passive or planar systems, driven by activity and geometry.
• Discovery of a novel rotating spiral defect characteristic of active smectic systems on spheres, which dictates the steady state.

Conclusions:

• The dynamics of active smectic liquid crystals on spheres are significantly influenced by both intrinsic activity and the system's geometry.
• The spherical confinement leads to accelerated defect coarsening and the emergence of unique defect structures.
• The findings provide a theoretical framework that can be experimentally validated using dense systems of synthetic or biological active particles.