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SUMMARY:Some recent results on the interaction between two order parameter
 s : the case of linear-quadratic coupling - Ekhard Salje (Department of Ea
 rth Sciences)
DTSTART:20111107T161500Z
DTEND:20111107T170000Z
UID:TALK34477@talks.cam.ac.uk
CONTACT:Ian Farnan
DESCRIPTION:The coupling between order parameters in systems with several 
 instabilities has been analyzed within Landau theory. The dominant term co
 nsidered in this paper is linear in one order parameter and quadratic in t
 he second order parameter ~ QP2\, other coupling terms have been treated p
 reviously. Typical examples for Q are proper or pseudo-proper ferroelastic
  instabilities\, while P might be octahedral tilting in a perovskite\, (an
 ti-) ferromagnetic ordering or (anti) ferroelectric soft modes. Coupling o
 f this type is common in fluorites\, Verwey transitions\, Jahn Teller syst
 ems\, pnictide super conductors etc. Analytical solutions and characterist
 ic phase diagrams of the stable configurations are compiled. The coupling 
 can lead to stepwise phase transitions even when the uncoupled systems wou
 ld show continuous transitions.  Mixed phase are common\, so that many ‘
 intermediate phases’ described in literature are in fact the result of t
 his linear-quadratic coupling.\n
LOCATION:Harker 2 lecture room\, Department of Earth Sciences\, Downing Si
 te
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