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Collisions of monopoles, disclinations and dislocations
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Resumo(s)
Motions and collisions of topological defects produced during symmetry breaking transitions is a crucial issue in cosmology and in condensed matter physics. Here, we deal with topological defects in nematics and cholesterics. Nematics may contain linear defects i.e. disclinations and point defects i.e. monopoles while cholesterics may contain linear defects of their 1D periodic order parameter, i.e. dislocations. The dowser texture appears as a natural universe of the nematic monopoles. They can be generated in it, set into motion and brought to collisions that may result in annihilation of pairs of monopoles. We show how to generate pairs of disclinations in twisted nematic cells by the isotropic-nematic transition in the presence of magnetic fields. When two such disclinations collide, i.e. enter into a contact at one point, an intercommutation or rewiring into a new pair of disclination can occur. We show how to bring these disclinations to collisions by means of an electric field and how to steer the rewiring by magnetic fields. For generation of dislocations in cholesteric we use a Grandjean–Cano wedge made of crossed cylindrical mica sheets. After their nucleation upon dilation, dislocation loops are growing and collide. Collision of dislocation loops can result in a trivial crossing or may produce a stable configuration called Lehmann cluster. Subsequently, upon application of a high enough tensile strain, the Lehmann splits into a pair of dislocations that can be entangled.
Descrição
Funding Information: M. H. G and P. P. are grateful to Arne Skjeltorp for invitation to the Geilo School 2022. The authors thank V. Klein, S. Saranga, J. Sanchez, Y. Simon, J. Saen, J.-L. Signoret and M. Bottineau for technical help. We also thank M. Zeghal, P. Judeinstein and C. Goldmann for discussions and help. Rapid progresses in experiments presented here were made during internships of M. Dazza, R. Cabeça, G. Srinivasan, J. Plo, D. Sadi, E. Thellier, T. Alezraa, A. Goré, A.Safi, R. Bouffet-Klein, B. Liagre, and N. Rouger. M.H.G. acknowledges the co-financement by FEDER, European fuand in condensed matter physicsnds, through the COMPETE 2020 POCI and PORL, National Funds through FCT Portuguese Foundation for Science and Technology and POR Lisboa2020 under projects PIDDAC (POCI-01-0145-FEDER-007688, Reference UIDB/50025/2020-2023), Action European Topology Interdisciplinary Action (EUTOPIA CA17139). Publisher Copyright: © The Author(s), under exclusive licence to EDP Sciences, Springer-Verlag GmbH Germany, part of Springer Nature 2024.
Palavras-chave
General Materials Science General Physics and Astronomy Physical and Theoretical Chemistry