Figure 1: Elastic hexadecapole induced by a colloidal PSM.
From: Hexadecapolar colloids
(a–d) Optical micrographs obtained with (a,b) POM and (c,e) bright field microscopy. P, A and γ mark the crossed polarizer, analyser and a slow axis of a 530 nm retardation plate (aligned at 45° to P and A), respectively. (d) Schematic diagram of induced n(r) (green rods) satisfying the tilted boundary conditions at the PSM surface (red rods), with the ‘easy axis’ at a constant angle ψe to a local normal s to the surface (black rods). (f) Schematic of conic degenerate surface boundary conditions. (g,h) Three-dimensional visualization of the x-component nx of n(r) (g) at the surface of PSM for ψe=45° and (h) at a spherical surface of radius 1.2r0 shown using a dashed red circle in d. Blue, yellow and magenta colours correspond, respectively, to a positive, near-zero and negative nx according to the colour scheme shown in g. Dashed equatorial line in d and a black solid line in g depict the ‘Saturn ring’ surface defect loop at the particle’s equator visible in c. Black hemispheres in d and g show surface point defects boojums at the poles of the particle visible in e. Scale bars, 2 μm.
