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UID:1-488@lptms.universite-paris-saclay.fr
DTSTART:20170221T110000Z
DTEND:20170221T120000Z
DTSTAMP:20170206T131610Z
URL:http://www.lptms.universite-paris-saclay.fr/seminars/seminaire-du-lptm
 s-beatriz-seoane-bartolome-2/
SUMMARY:Séminaire du LPTMS: Beatriz Seoane Bartolomé - LPTMS\, salle 201\
 , 2ème étage\, Bât 100\, Campus d'Orsay - 21 Fév 17 11:00
DESCRIPTION:Matching experiments and theory in spin glasses\nBeatriz Seoane
  Bartolomé (LPT-ENS\, Paris)\nThe unifying feature of glass formers (such
  as polymers\, supercooled liquids\, colloids\, granular materials\, spin 
 glasses\, superconductors\, ...) is a sluggish dynamics at low temperature
 s. Indeed\, their dynamics is so slow that thermal equilibrium is never re
 ached in macroscopic samples: in analogy with living beings\, glasses are 
 said to age. This fact suppose a difficulty to describe these systems theo
 retically. The reasons are two fold. One the one hand\, most of the calcul
 ations are obtained in the experimentally unreachable low-temperature equi
 librium\, and on the other hand\, they concern microscopic observables (ob
 tained mainly with the replica method) that are hard to measure in experim
 ents. In two recent works [1\,2]\, we have shown that it is possible to qu
 antitatively relate both realms\, using large-scale simulations on the sp
 ecial-purpose computers Janus and Janus II\, two dedicated supercomputers 
 to simulate spin-glasses.\n\nIn the first work [1]\, we have performed a v
 ery accurate computation of the non-equilibrium fluctuation-dissipation ra
 tio for the three-dimensional Edwards-Anderson Ising spin glass. This rati
 o (computed for finite times on very large\, effectively infinite\, system
 s) is compared with the equilibrium probability distribution of the spin o
 verlap for finite sizes. The resulting quantitative statics-dynamics dict
 ionary\, based on observables that can be measured with current experiment
 al methods\, could allow the experimental exploration of important feature
 s of the spin-glass phase without uncontrollable extrapolations to infinit
 e times or system sizes.\n\nOn the other hand\, in Ref. [2]\, we have rep
 roduced in simulations a milestone experiment that measures the spin-glass
  coherence length through the lowering of free-energy barriers induced by
  the Zeeman effect. Secondly we determine the scaling behavior that allows
  a quantitative analysis of a new experiment of amorphous Ge:Mn films [3].
   The value of the coherence length estimated through the analysis of mic
 roscopic correlation functions turns out to be quantitatively consistent w
 ith its measurement through macroscopic response functions. Further\, non-
 linear susceptibilities\, recently measured in glass-forming liquids\, sca
 le as powers of the same microscopic length.\n[1] Janus Collaboration (201
 7)\, ``Probing the spin-glass phase with non-equilibrium measurements: sta
 tics-dynamics equivalence through the fluctuation-dissipation ratio''\, ac
 cepted for PNAS\, https://arxiv.org/abs/1610.01418\n[2] Janus Collaborati
 on (2017)\, ``Matching microscopic and macroscopic responses in glasses''\
 , under review in PRL.\n[3] Samaresh Guchhait and Raymond L. Orbach (2017)
 \, ``Magnetic Field Dependence of Spin Glass Free Energy Barriers''\, unde
 r review in PRL.
CATEGORIES:seminars
LOCATION:LPTMS\, salle 201\, 2ème étage\, Bât 100\, Campus d'Orsay\, 15 
 Rue Georges Clemenceau\, Orsay\, 91405\, France
GEO:48.698185;2.181768
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=15 Rue Georges Clemenceau\,
  Orsay\, 91405\, France;X-APPLE-RADIUS=100;X-TITLE=LPTMS\, salle 201\, 2è
 me étage\, Bât 100\, Campus d'Orsay:geo:48.698185,2.181768
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