The topology of non-uniform media in condensed matter physics

Trebin, Hans‐Rainer

doi:10.1080/00018738200101458

Cited by 208 publications

(127 citation statements)

References 79 publications

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“…Such colloidal dimers then interact with each other and assemble into a square two-dimensional colloidal crystal. The emergence of topological defects in nematic colloids is not only important for the interaction and binding of colloidal particles into stable and geometrically regular structures, as demonstrated in a number of studies; they are interesting objects by themselves [23][24][25]. The topological defects in nematic LCs are reminiscent of the phenomenon of the electric charge, because they seem to obey the law of conservation of the topological charge [26].…”

Section: Photonic Crystals Made Of Liquid Crystals and Colloidsmentioning

confidence: 99%

Nematic colloids, topology and photonics

Muševič

2013

Phil. Trans. R. Soc. A.

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We review and discuss recent progress in the field of nematic colloids, with an emphasis on possible future applications in photonics. The role of the topology is described, based on experimental manipulations of the topological defects in nematic colloids. The topology of the ordering field in nematics provides the forces between colloidal particles that are unique to these materials. We also discuss recent progress in the new field of active microphotonic devices based on liquid crystals (LCs), where chiral nematic microlasers and tuneable nematic microresonators are just two of the recently discovered examples. We conclude that the combination of topology and microphotonic devices based on LCs provides an interesting platform for future progress in the field of LCs.

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Section: Photonic Crystals Made Of Liquid Crystals and Colloidsmentioning

confidence: 99%

Nematic colloids, topology and photonics

Muševič

2013

Phil. Trans. R. Soc. A.

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“…A powerful feature of homotopy theory is the ability to classify the topological defects based on the relationship between the initial and final symmetries [18][19][20][21][22][23]. This is achieved by mapping the high-and low-symmetry groups onto topological spaces and classifying the relationship between them in terms of its homotopy group.…”

Section: Classification Of Topological Defectsmentioning

confidence: 99%

On the relationship between topological and geometric defects

Griffin

Spaldin

2017

J. Phys.: Condens. Matter

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“…Topological defects [26,77] abound systems with broken symmetries: in ordered media like magnetic materials, crystalline materials -both solids and liquids, in superfluid helium, and in quantum Hall fluids [45,[78][79][80][81][82][83][84]. Owing to the similarities in nature of the scaling laws characterizing such systems, liquid crystals provide an easily accessible platform for investigations.…”

Section: Topological Defectsmentioning

confidence: 99%

Nematic Liquid Crystals and Nematic Colloids in Microfluidic Environment

Sengupta

Herminghaus

Bahr

2011

Molecular Crystals and Liquid Crystals

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Where the mind is without fear and the head is held high;Where knowledge is free;Where the world has not been broken up into fragments by narrow domestic walls;Where words come out from the depth of truth;Where tireless striving stretches its arms towards perfection;Where the clear stream of reason has not lost its way into the dreary desert sand of dead habit;Where the mind is led forward by thee into ever-widening thought and actionInto that heaven of freedom, my Father, let my country awake.Rabindranath Tagore (1861Tagore ( -1941 To my parents, my brother, and all the sacrifices they made for me AbstractThe doctoral thesis presented here is one of the first systematic attempts to unravel the wonderful world of liquid crystals within microfluidic confinements, typically channels with dimensions of tens of micrometers. The present work is based on experiments with a roomtemperature nematic liquid crystal, 5CB, and its colloidal dispersions within microfluidic devices of rectangular cross-section, fabricated using standard techniques of soft lithography. To begin with, a combination of physical and chemical methods was employed to create well defined boundary conditions for investigating the flow experiments. The walls of the microchannels were functionalized to induce different kinds of surface anchoring of the 5CB molecules: degenerate planar, uniform planar, and homeotropic surface anchoring. Channels possessing composite anchoring conditions (hybrid) were additionally fabricated, e. g. homeotropic and uniform planar anchoring within the same channel. On filling the microchannels with 5CB in the isotropic phase, different equilibrium configurations of the nematic director resulted, as the sample cooled down to nematic phase. For a given surface anchoring, the equilibrium director configuration varied also with the channel aspect ratio. The static director field within the channel registered the initial conditions for the flow experiments. The static and i ii dynamic experiments have been analyzed using a combination of polarization, and confocal fluorescence microscopy techniques, along with particle tracking method for measuring the flow speeds. Additionally, dual-focus fluorescence correlation spectroscopy is introduced as a generic velocimetry tool for liquid crystal flows.The flow of nematic liquid crystals is inherently complex due to the coupling between the flow and the nematic director. The presence of the four confining walls and the nature of surface anchoring on them complicate the flow-director interactions further. In microchannels possessing degenerate planar anchoring, four different flow-induced defect textures were identified with increasing Ericksen number: π-walls, disclination lines pinned to the channel walls, disclination lines with one pinned and one freely suspended end, and disclination loops freely flowing in a chaotic manner. However, such textures and sequence of defects were not observed for flows within channels with homogeneous anchoring.Using experiments and numerical modeling...

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The topology of non-uniform media in condensed matter physics

Cited by 208 publications

References 79 publications

Nematic colloids, topology and photonics

Nematic colloids, topology and photonics

On the relationship between topological and geometric defects

Nematic Liquid Crystals and Nematic Colloids in Microfluidic Environment

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