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SUMMARY:Tunable States in a Model Quantum Magnet
DTSTART:20160324T113000
DTEND:20160324T123000
DTSTAMP:20260408T025927Z
UID:30c24fd54d6d92a685f7bc51a8e9b620786690d4283c325a7fc5fee3
CATEGORIES:Conferences - Seminars
DESCRIPTION:Daniel M. Silevitch\, Caltech\, Pasadena\, USA\nChanging the g
 round state of a system via a non-thermal parameter such as doping or pres
 sure has been a topic of great interest in condensed matter physics for de
 cades\, most notably in the study of quantum phase transitions and the ass
 ociated quantum critical regime. The rare-earth fluoride LiHoF_4 and the r
 elated dilution series LiHo_{1-x}Y_xF4\, long known to be a realization of
  the S=1/2 Transverse Ising Model\, can be used to study state tuning as a
  function of several tuning parameters. In addition to the well-understood
  field-induced ferromagnet to paramagnet quantum phase transition in pure 
 LiHoF_4\, there are a number of subtler transitions which are seen in the 
 diluted materials. For x~=0.5\, application of a magnetic field transverse
  to the Ising axis transitions the system into a realization of the Random
 -Field Ising Model\, an important generic model for studying the effects o
 f disorder. In the more highly dilution limit\, at x~0.05\, ordered ferrom
 agnetic states are no longer stable due to frustration effects. Instead\, 
 the system shows behavior consistent with either a spin glass or a non-fre
 ezing spin liquid\, and can be tuned between these two regimes by varying 
 the degree of thermal connectivity with an external heat bath or by tuning
  the rate of quantum tunneling via an external magnetic field. Further\, t
 he behavior of nonlinear excitations can be continuously tuned by external
  fields\, including the ability to largely decouple the excitations from t
 he background spin environment.
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STATUS:CONFIRMED
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