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SUMMARY:Topological defect formation in a nematic undergoing an extreme te
 mperature quench - Igor Musevic (Jozef Stefan Institute\; University of Lj
 ubljana  )
DTSTART:20190516T080000Z
DTEND:20190516T084000Z
UID:TALK124546@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:The Kibble-Zurek mechanism (KZM) describes the formation of to
 pological defects during the rapid crossing of a second-order phase transi
 tion. Several experiments have been performed using nematic liquid crystal
 s\, 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 m
 echanism 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 t
 ransition 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 princi
 ple. We have developed a novel illumination technique that can take instan
 taneous images of the quenched sample area with an exposure time of 20 nan
 oseconds. We have also developed a technique to measure the time dependenc
 e of the temperature during the quench. This makes it possible to study de
 fect formation with very accurate timing and an accurate measurement of th
 e local temperature during the quench. The robustness of the experiment al
 lows for several thousand repetitions\, which can greatly improve the stat
 istics of the measurements. The current status of the experiments is repor
 ted. Coauthored by Uros Jagodic and Anna V. Ryzhkova.
LOCATION:Seminar Room 1\, Newton Institute
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