Commensurate states and pattern switching <i>via</i> liquid crystal skyrmions trapped in a square lattice

Duzgun, Ayhan; Nisoli, Cristiano; Reichhardt, C.

doi:10.1039/c9sm02312g

Cited by 29 publications

(20 citation statements)

References 50 publications

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“…Numerical Modeling and Visualization of Topological Structures: Topological structures in chiral LC-GNPB were modeled by numerically minimizing the Frank-Oseen free energy functional [1,25,38]…”

Section: Methodsmentioning

confidence: 99%

Nematic Order, Plasmonic Switching and Self‐Patterning of Colloidal Gold Bipyramids

et al. 2021

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Dispersing inorganic colloidal nanoparticles within nematic liquid crystals provides a versatile platform both for forming new soft matter phases and for predefining physical behavior through mesoscale molecular-colloidal self-organization. However, owing to formation of particle-induced singular defects and complex elasticity-mediated interactions, this approach has been implemented mainly just for colloidal nanorods and nanoplatelets, limiting its potential technological utility. Here, orientationally ordered nematic colloidal dispersions are reported of pentagonal gold bipyramids that exhibit narrow but controlled polarization-dependent surface plasmon resonance spectra and facile electric switching. Bipyramids tend to orient with their C 5 rotation symmetry axes along the nematic director, exhibiting spatially homogeneous density within aligned samples. Topological solitons, like heliknotons, allow for spatial reorganization of these nanoparticles according to elastic free energy density within their micrometer-scale structures. With the nanoparticle orientations slaved to the nematic director and being switched by low voltages ≈1 V within a fraction of a second, these plasmonic composite materials are of interest for technological uses like color filters and plasmonic polarizers, as well as may lead to the development of unusual nematic phases, like pentatic liquid crystals.

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Section: Methodsmentioning

confidence: 99%

Nematic Order, Plasmonic Switching and Self‐Patterning of Colloidal Gold Bipyramids

et al. 2021

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“…Although self-organization of nontrivial structures in a simple setup is interesting in its own right, more complex setup, particularly by surface patterning and/or non-planar surface geometry, brings about a richer possibility of arranging and manipulating (half-)Skyrmions. [155][156][157][158][159] Such broader freedom of the arrangement of (half-)Skyrmions could find applications, in particular optical ones as we will mention below.…”

Section: Discussionmentioning

confidence: 99%

Liquid Crystalline Half‐Skyrmions and Their Optical Properties

et al. 2022

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Liquid crystals have intrigued physicists as a platform that facilitates direct visualization of topological concepts. Here, the theoretical and experimental studies demonstrating that a thin film of a chiral liquid crystal forms topological entities known as half-Skyrmions, swirl-like orientational order that spans the hemisphere of the order parameter space S 2 ∕Z 2 , are reviewed. They appear in the form of a hexagonal lattice or in an isolated manner, accompanied by topological line defects to satisfy topological constraints. Under an optical microscope, half-Skyrmions appear as dark spots, and their hexagonal lattice yields a Kossel diagram comprising a hexagonal arrangement of circular arcs. These experimental observations are corroborated by numerical calculations of the orientational order based on the Landau-de Gennes theory with an orientational order parameter of a second-rank tensor, and construction of its optical images and Kossel diagrams by directly solving Maxwell equations for light wave. A thin film of a chiral liquid crystal thus provides an interesting system for the investigation of topological concepts, and spontaneous formation of a half-Skyrmion lattice whose periodicity is of the order of the wavelength of visible light has a potential for photonics applications as well as poses a challenging problem on optics.

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“…We consider a single liquid crystal skyrmion under two oscillating fields using continuum based simulations of the type employed previously to model LC skyrmions [10,24,25]. In the continuum description, the traceless tensor Q relates the scalar order parameter S to the orientational order of a chiral nematic liquid crystal state, which under proper constraints will support skyrmions in systems confined between two substrates with normal surface anchoring.…”

Section: Methodsmentioning

confidence: 99%

“…, where F = f (r)d 3 r and Γ is the mobility constant. As in previous work [10,24,25] we employ z-invariant (2D) skyrmions [26]. The out of plane rotation of skyrmions is generated by tilting the background electric field.…”

Section: Methodsmentioning

confidence: 99%

Directed Motion of Liquid Crystal Skyrmions With Oscillating Fields

Duzgun,

Nisoli,

Reichhardt

et al. 2021

Preprint

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Using continuum simulations, we show that under a sinusoidal electric field, liquid crystal skyrmions undergo periodic shape oscillations which produce controlled directed motion. The speed of the skyrmion is non-monotonic in the frequency of the applied field, and exhibits multiple reversals of the motion as a function of changing frequency. We map out the dynamical regime diagram of the forward and reverse motion for two superimposed ac driving frequencies, and show that the reversals and directed motion can occur even when only a single ac driving frequency is present. Using pulsed ac driving, we demonstrate that the motion arises due to an asymmetry in the relaxation times of the skyrmion shape. We discuss the connection between our results and ratchet effects observed in systems without asymmetric substrates.

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Commensurate states and pattern switching via liquid crystal skyrmions trapped in a square lattice

Cited by 29 publications

References 50 publications

Nematic Order, Plasmonic Switching and Self‐Patterning of Colloidal Gold Bipyramids

Nematic Order, Plasmonic Switching and Self‐Patterning of Colloidal Gold Bipyramids

Liquid Crystalline Half‐Skyrmions and Their Optical Properties

Directed Motion of Liquid Crystal Skyrmions With Oscillating Fields

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