Dresden 2020 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 24: Complex Fluids and Soft Matter (joint session DY/CPP)

DY 24.6: Vortrag

Dienstag, 17. März 2020, 10:45–11:00, ZEU 160

Defect annihilation 2D using free-standing smetic films — •Kirsten Harth1, Amine Missaoui1, Peter Salamon2, and Ralf Stannarius11Institut für Physik, Otto-von-Guericke Universität Magdeburg — 2Department of Complex Fluids, Wigner Research Center, Budapest, Hungary

Interacting defects in quasi-2D geometries occur in manifold systems, from strings in cosmology over spin systems in Bose-Einstein condensates or thin magnetic films to liquid crystals. Free-standing smecti C films (smC FSF) represent a quite simple sytem for studying fluid mechanics and pattern formation in 2D. They are particularly easy to handle and orientational patterns are directly observable using polarizing microscopy, but few experiments exist so far. Theory is either fully numerical or focuses on very simplified situations. Orientational problems among the defects and with the far director field were only recently noticed.

With a special method, we are able to prepare isolated pairs of +1 and -1 defects in homogeneous smC FSF, and we study their annihilation. Aligned defect pairs qualitatively follow expectations from theory and approach on straight paths. Misoriented defects pairs display curved trajectories, and their dynamics quantitatively disagrees with theoretical predictions[1]. We discuss experimental findings and possible explanations for the discrepancies.

[1] X. Tang and J. V. Selinger, Soft Matter 13, 5481 (2017)

[2] A. Missaoui, K. Harth, P. Salamon, R. Stannarius, arXiv:1911.05224

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