期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 110, 期 23, 页码 9231-9236出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1301464110
关键词
colloids; low-dimensional topology; elasticity; topological theorems; disclinations
资金
- National Science Foundation [DMR-0847782, DMR-0820579, DMR-0844115]
- 7th Framework Programme International Research Staff Exchange Scheme Marie-Curie Grant [PIRSES-GA-2010-269181]
- Direct For Mathematical & Physical Scien [GRANTS:13632038] Funding Source: National Science Foundation
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [0844115] Funding Source: National Science Foundation
- Division Of Materials Research [GRANTS:13632038] Funding Source: National Science Foundation
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [GRANTS:13707490, 0847782] Funding Source: National Science Foundation
Topological defects that form on surfaces of ordered media, dubbed boojums, are ubiquitous in superfluids, liquid crystals (LCs), Langmuir monolayers, and Bose-Einstein condensates. They determine supercurrents in superfluids, impinge on electrooptical switching in polymer-dispersed LCs, and mediate chemical response at nematic-isotropic fluid interfaces, but the role of surface topology in the appearance, stability, and core structure of these defects remains poorly understood. Here, we demonstrate robust generation of boojums by controlling surface topology of colloidal particles that impose tangential boundary conditions for the alignment of LC molecules. To do this, we design handlebody-shaped polymer particles with different genus g. When introduced into a nematic LC, these particles distort the nematic molecular alignment field while obeying topological constraints and induce at least 2g - 2 boojums that allow for topological charge conservation. We characterize 3D textures of boojums using polarized nonlinear optical imaging of molecular alignment and explain our findings by invoking symmetry considerations and numerical modeling of experiment-matching director fields, order parameter variations, and nontrivial handle-shaped core structure of defects. Finally, we discuss how this interplay between the topologies of colloidal surfaces and boojums may lead to controlled self-assembly of colloidal particles in nematic and paranematic hosts, which, in turn, may enable reconfigurable topological composites.
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