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SUMMARY:Patterns of co-existing order parameters and universal escapeway t
 o the  magnetic quantum critical point - Prof. Georgios Varelogiannis\, Na
 tional Technical University of Athens
DTSTART:20081127T130000Z
DTEND:20081127T140000Z
UID:TALK15437@talks.cam.ac.uk
CONTACT:Tracey Ingham
DESCRIPTION:We show that particle-hole asymmetry induced by doping or pres
 sure leads to patterns of order parameters that necessarily coexist whenev
 er two of the order parameters are present. \nWe have found a systematic w
 ay to predict all such patterns of unconventional superconducting and part
 icle-hole condensates. \nWe report novel magnetic field induced transition
 s to the multiphase pattern states that exhibit some of the \nthermodynami
 c characteristics of Fulde-Ferrel phases. \nFor example\, above a given fi
 eld\, we report a transition from d-wave singlet SC to a state in which d-
 wave singlet SC coexists with staggered triplet SC and SDW\nthe other two 
 partners of the given pattern.\nWe will argue based on experiments on CeCo
 In_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 with Fulde-Ferrel signatu
 res to a state in which CDW\, SDW and FM all coexist.\nDouble step metamag
 netic transitions in bilayered ruthenites and other materials as well as h
 idden orders like in URu_2Si_2 can all be understood in this context.\nBy 
 reporting similar results on these two examples of completely different ph
 ysical situations we will argue that these "Fulde-Ferrel"-like transitions
  to the multiphase state may represent a universal escapeway to the magnet
 ic quantum critical point.\nWe may verify this conjencture on additional p
 atterns.\n\nFor some related Refs. see e.g.\narxiv:0804.2450\; arxiv:0804.
 2460\; arxiv:0802.4093\; arxiv:0709.1025\; arxiv:0802.4080
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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