26ème Congrès Général de la SFP

Topological metadefects: tangles of dislocations

Non programmé

20m

Centre des Congrès de la Villette (Cité des sciences et de l'Industrie, Paris)

Poster MC15 Matière molle : des concepts fondamentaux à la fabrication de systèmes originaux Session Poster 1: MC3, MC5, MC6, MC11, MC13, MC15, MC16, MC18, MC19, MC25, REDP, posters hors MC

Orateur

Pawel Pieranski (Laboratoire de Physique des Solides, Université Paris-Saclay, France)

Description

Topological defects such as vortices, dislocations or disclinations are fingerprints of order parameters resulting from broken symmetries. We introduce the new concept of topological defects of a higher order, that we propose to call metadefects, using as a generic example tangles of dislocations in cholesterics.

Tangles of dislocations are generated by a tensile strain in a cholesteric layer confined by capillarity between crossed cylindrical sheets.

Primary tangles result from the overlapping instability that breaks the D2 symmetry of the coplanar dislocations’ pair called Lehmann cluster.

Upon a further application of the tensile strain, the primary tangles can be iteratively wound up into dextrogyre and levogyre helical pairs of dislocations conjectured formerly by Kleman, Friedel and Bouligand [2,3].

[1] P. Pieranski and M.H. Godinho, Collisions of monopoles, dislocations and monopoles, to appear in Proceedings of the Geilo School 2022 published by EPJST (2023).
[2] M. Kleman and J. Friedel, Lignes de dislocations dans les cholestériques, Journal de Physique Colloques 30 (1969) C4-43—C4-53.
[3] Y. Bouligand and M. Kleman, Paires de disinclinaisons hélicoïdales dans les cholestériques, Journal de Physique 31 ( 1970) 1041-1054.