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Topological defect formation in a nematic undergoing an extreme temperature quench

Presented by: 
Igor Musevic Jozef Stefan Institute, University of Ljubljana
Thursday 16th May 2019 - 09:00 to 09:40
INI Seminar Room 1
The Kibble-Zurek mechanism (KZM) describes the formation of topological defects during the rapid crossing of a second-order phase transition. Several experiments have been performed using nematic liquid crystals, with the aim being to observe the KZM. Most of the experiments report on the late-stage coarsening dynamics of the defect tangle, whereas the mechanism of defect formation in the early stage is still not convincingly demonstrated and lacks solid evidence. We have designed an experiment that can generate an extremely rapid crossing of the isotropic-nematic phase transition which currently achieves cooling rates in excess of 40,000 K/s, with cooling rates as fast as 1,000,000 K/s being achievable in principle. We have developed a novel illumination technique that can take instantaneous images of the quenched sample area with an exposure time of 20 nanoseconds. We have also developed a technique to measure the time dependence of the temperature during the quench. This makes it possible to study defect formation with very accurate timing and an accurate measurement of the local temperature during the quench. The robustness of the experiment allows for several thousand repetitions, which can greatly improve the statistics of the measurements. The current status of the experiments is reported. Coauthored by Uros Jagodic and Anna V. Ryzhkova.
University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons