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SUMMARY:Patterns of coexisting order parameters and universal escapeway to
  the magnetic quantum critical point - Professor Georgios Varelogiannis\, 
 National Technical University of Athens
DTSTART:20081127T130000Z
DTEND:20081127T140000Z
UID:TALK15424@talks.cam.ac.uk
CONTACT:Tracey Ingham
DESCRIPTION:We show that particle-hole asymmetry induced by doping or pres
 sure\nleads to patterns of order parameters that necessarily coexist whene
 ver\ntwo of the order parameters are present. \nWe have found a systematic
  way to predict all such patterns\nof unconventional superconducting and p
 article-hole condensates. \nWe report novel magnetic field induced transit
 ions to the multiphase pattern states that exhibit some of the \nthermodyn
 amic characteristics of Fulde-Ferrel phases. \nFor example\, above a given
  field\, \nwe report a transition from d-wave singlet SC to a \nstate in w
 hich d-wave singlet SC coexists with staggered triplet SC and SDW\nthe oth
 er two partners of the given pattern.\nWe will argue based on experiments 
 on CeCoIn_5 that this may correspond to the\nhigh field so called "Q-phase
 " state observed in this material.\nA very similar behavior is obtained in
  a CDW system where we report field induced transitions\nwith Fulde-Ferrel
  signatures to a state in which CDW\, SDW and FM all coexist.\nDouble step
  metamagnetic transitions in bilayered ruthenites and other materials as w
 ell\nas hidden orders like in URu_2Si_2 can all be understood in this cont
 ext.\nBy reporting similar results on these two examples of completely dif
 feremt physical situations\nwe will argue that these "Fulde-Ferrel"-like t
 ransitions to the multiphase state\nmay represent a universal escapeway to
  the magnetic quantum critical point.\nWe may verify this conjencture on a
 dditional patterns.\n\nFor some related Refs. see e.g.\narxiv:0804.2450\; 
 arxiv:0804.2460\; arxiv:0802.4093\; arxiv:0709.1025\; arxiv:0802.4080\n
LOCATION:TCM Seminar Room\, Mott Building Room 530\, Cavendish Laboratory
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