Topology and Geometry of Smectic Order on Compact Curved Substrates

TL;DR

This paper uses differential forms to classify and analyze low energy smectic states on curved surfaces like spheres and tori, revealing topological distinctions, state counts, and disclination dynamics.

Contribution

It introduces a differential form formalism to systematically classify smectic states on curved substrates and explores their topological and energetic properties.

Findings

Number of low energy states scales as the square root of system area.

Different topological states are not connected by local fluctuations.

Disclination motion on spheres relates to elliptic function theory.

Abstract

Smectic order on arbitrary curved substrate can be described by a differential form of rank one (1-form), whose geometric meaning is the differential of the local phase field of the density modulation. The exterior derivative of 1-form is the local dislocation density. Elastic deformations are described by superposition of exact differential forms. We use the formalism of differential forms to systematically classify and characterize all low energy smectic states on torus as well as on sphere. A two dimensional smectic order confined on either manifold exhibits many topologically distinct low energy states. Different states are not accessible from each other by local fluctuations. The total number of low energy states scales as the square root of the system area. We also address the energetics of 2D smectic on a curved substrate and calculate the mean field phase diagram of smectic on a thin torus. Finally, we discuss the motion of disclinations for spherical smectics as low energy excitations, and illustrate the interesting connection between spherical smectic and the theory of elliptic functions.