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SUMMARY:Driving a glass to flow: how X-rays reveal the dynamics of an amor
 phous material
DTSTART:20261014T100000Z
DTEND:20261014T110000Z
DTSTAMP:20261024T162400Z
UID:indico-event-1953@indico.dfa.unipd.it
DESCRIPTION:Speakers: Lara Piemontese (UniPD)\n\nGlasses are among the mos
 t widespread yet least understood materials in condensed matter physics. R
 igid like solids at the atomic scale\, yetstructurally disordered like liq
 uids\, they exist in a perpetual state of arrested relaxation — frozen f
 ar from equilibrium\, slowly evolving ontimescales that can exceed the age
  of the universe.How can we drive a glass out of this arrested state? And 
 how does it respond when we continuously push it out of equilibrium?We exp
 lore these questions choosing\, among the different kinds of external pert
 urbations\, a rather unusualtool: an X-ray beam. It is indeed known that a
  focused synchrotron X-ray beam can do something unexpected: itdoes not me
 rely probe a glass\, but it drives it. We show that hard X-ray photons abs
 orbed by GeSe₂ samplestrigger localized bond-breaking events and generat
 e coordination defects. Under sustained irradiation\, theglass undergoes a
  transition from a solid-like\, elastically responding state to a plastica
 lly flowing state.Importantly\, in this game the beam is used both as a so
 urce of dynamics and as a way of watching thatdynamics in real time. This 
 is made possible by X-ray Photon Correlation Spectroscopy (XPCS) technique
 .Its combination with Fast Differential Scanning Calorimetry (FDSC) allows
  us to study how this beam-inducedmotion changes with temperature\, from t
 he deep glassy state to and beyond the glass transition. At lowtemperature
 s\, the dynamics is mainly driven by the X-ray beam and increases with irr
 adiation rate. At hightemperatures\, instead\, the material's own thermal 
 relaxation dominates and the beam rate has little influence.In between\, t
 he two processes compete: irradiation tends to rejuvenate the glass\, whil
 e temperature allows it torelax and anneal. This competition leads to a su
 rprisingly rich picture of glassy dynamics\, where the materialdoes not si
 mply become "more liquid" under irradiation. Instead\, its response depend
 s on temperature\,irradiation history\, and the balance between externally
  induced rearrangements and intrinsic relaxation.\n\nhttps://indico.dfa.un
 ipd.it/event/1953/
LOCATION:P2D (Dipartimento di Fisica e Astronomia - Edificio Ricci-Curbast
 ro (ex-Paolotti))
URL:https://indico.dfa.unipd.it/event/1953/
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