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TZID:Europe/Paris
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BEGIN:VEVENT
UID:0-715@lptms.universite-paris-saclay.fr
DTSTART:20200114T110000Z
DTEND:20200114T120000Z
DTSTAMP:20200111T144518Z
URL:http://www.lptms.universite-paris-saclay.fr/seminars/seminaire-du-lptm
 s-martial-mazars-lpt-u-psud/
SUMMARY:Séminaire du LPTMS: Martial Mazars (LPT U-PSUD) - Salle des sémin
 aires du FAST et du LPTMS\, bâtiment Pascal n°530 - 14 Jan 20 11:00
DESCRIPTION:Topological defects and the melting in two dimensions\nMartial 
 Mazars (LPT U-PSUD)\n\nTopological defects have a preponderant role in the
  physics of (quasi) two-dimensional systems. One of the first applications
  is the description of the XY model by Kosterlitz and Thouless in the 1970
 s\; this theoretical description of the XY model made possible in the 1980
 s to formulate a theory for the fusion in two dimensions\, the KTHNY theor
 y (Kosterlitz - Thouless - Halperin - Nelson - Young). In KTHNY\, the tran
 sition from the solid phase to the liquid phase occurs with an intermediat
 e phase\, the hexatic phase\, and each of the transitions: solid / hexatic
  and hexatic / liquid is of the KT type.\nThe microscopic mechanisms in KT
 HNY leading to phase transitions are dissociations of clusters of topologi
 cal defects: the dissociation of dislocation pairs into free dislocations 
 (solid / hexatic) and the dissociation of dislocations into free disclinat
 ions (hexatic / liquid). This description of the two-dimensional fusion is
  in competition with a first-order transition between solid and liquid\, w
 ithout hexatic phase.\nThe existence of an intermediate hexatic phase for 
 simple systems in two dimensions remained hypothetical until the mid-2000s
  when it was observed in experiments on superparamagnetic colloids confine
 d to a water-air interface (Keim\, Maret 2007). This observation reinforce
 s the relevance of KTHNY. Then\, with computer simulations of hard disks (
 Krauth - 2011) and in colloidal systems (Thorneywork\, Dullens - 2017)\, t
 he hexatic / liquid transition is found to be first order\, in contradicti
 on with KTHNY.\nIn this seminar\, we show that the mechanisms of dissociat
 ion of the KTHNY topological clusters are responsible for the solid / hexa
 tic and hexatic / liquid transitions\, and that\, by a statistical analysi
 s of the topological clusters\, the KTHNY theory is compatible with a firs
 t order transition for the hexatic / liquid.\n\nReferences : \n- P. Keim\,
  G. Maret and H.H. von Grünberg\, 2007\, Phys. Rev. E.\, 75\, 031402.\n- 
 E.P. Bernard\, W. Krauth\, 2011\, Phys. Rev. Lett.\, 107\, 155704.\n- A. L
 . Thorneywork\, J. L. Abbott\, D. G. A. L. Aarts and R. P. A. Dullens\, 20
 17\, Phys. Rev. Lett.\, 118\, 158001.\n\nThe results presented in this sem
 inar have been published in :\n- M. Mazars\, 2015\, EPL\, 110\, 26003. \n-
  M. Mazars and R. Salazar\, 2019\, EPL\, 126\, 56002. 
CATEGORIES:seminars
LOCATION:Salle des séminaires du FAST et du LPTMS\, bâtiment Pascal n°53
 0\, rue André Riviere\, Orsay\, 91405\, France
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=rue André Riviere\, Orsay\
 , 91405\, France;X-APPLE-RADIUS=100;X-TITLE=Salle des séminaires du FAST 
 et du LPTMS\, bâtiment Pascal n°530:geo:0,0
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