Topological Defects in Spherical Nematics

Abstract

We study the organization of topological defects in a system of nematogens confined to the two-dimensional sphere (S2). We first perform Monte Carlo simulations of a fluid system of hard rods (spherocylinders) living in the tangent plane of S2. The sphere is adiabatically compressed until we reach a jammed nematic state with maximum packing density. The nematic state exhibits four +1/2 disclinations arrayed on a great circle. This arises from the high elastic anisotropy of the system in which splay (K1) is far softer than bending (K3). We also introduce and study a lattice nematic model on S2 with tunable elastic constants and map out the preferred defect locations as a function of elastic anisotropy. We find a one-parameter family of degenerate ground states in the extreme splay-dominated limit K_{3}/K_{1}-->infinity. Thus the global defect geometry is controllable by tuning the relative splay to bend modulus.

Numerical insights into the phase diagram of p-atic membranes with spherical topology

“…4 for snapshots of equilibrated systems with ε = 10 and p = 1, 2, 3, 4. Our observations are in good agreement with previous theoretical predictions [25] and also with simulations of in-plane nematic fields (p = 2) on a spherical surface [37]. A quantitative verification of the description of Prost and Lubensky [25] is shown in fig.…”

Spatial separation in a thermal mixture of ultracoldYb174andRb87Baumer1, Münchow2, Görlitz3 et al. 2011Phys. Rev. A412470View full textAdd to dashboardCite

“…In trapped quantum degenerate gases this question of miscibility is determined by the interplay between single-species and interspecies interactions [5]. For such systems, phase separation has been observed in a dual species Bose-Einstein condensate with 87 Rb and 85 Rb [6] as well as in a strongly interacting Bose-Fermi mixture of Li 2 -molecules and 6 Li atoms [7]. In a dual-component gas of thermal atoms, the situation is somewhat different because the thermal motion, which counteracts interaction-driven spatial separation, has to be taken into account.…”

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