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SUMMARY:Pseudo-Goldstone modes and order-by-disorder - Jeffrey G. Rau (Uni
 versity of Windsor)
DTSTART:20230511T130000Z
DTEND:20230511T140000Z
UID:TALK197809@talks.cam.ac.uk
CONTACT:Bo Peng
DESCRIPTION:In systems with competing interactions\, continuous degeneraci
 es can appear which are accidental\, in that they are not related to any s
 ymmetry of the Hamiltonian. Accordingly\, the “pseudo”-Goldstone modes
  associated with these degeneracies are also unprotected. Indeed\, through
  a process known as “order-by-disorder” fluctuations can lift the dege
 neracy and induce a gap for these modes. In this talk\, I will discuss how
  these pseudo-Goldstone gaps arise in frustrated magnets when the fluctuat
 ions are (i) quantum mechanical and (ii) thermal in origin. I will show th
 at the gap can be exactly computed at leading order using an effective pic
 ture where the soft modes move in a potential generated by the fluctuation
 -induced free energy. Using explicit interacting spin-wave calculations an
 d direct numerical simulation\, I will illustrate and validate this framew
 ork for several key models of order-by-disorder. Finally\, I will discuss 
 some implications for candidate materials exhibiting order-by-disorder.
LOCATION:TCM Seminar Room
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