Accueil/ expose #carousel1 li{ width:150px; height:180px; } #carousel2 li{ width:150px; height:180px; } Solid Helium : Supersolidity or Quantum Plasticity ?
jeudi 24 novembre 2011
Loading the player... Descriptif

"Helium is a quantum material. Its zero point motion prevents it from freezing and liquid helium becomes a superfluid at temperatures below 2 K. It can be frozen by applying pressure but it is a very quantum mechanical solid. Over 40 years ago, it was predicted that helium could become a "supersolid" at low temperature — a solid in which crystalline order coexists with super ow. In 2004, experiments by Kim and Chan showed evidence that solid helium decouples from a torsional oscillator below 200 mK, the "non-classical rotational inertia" expected for a supersolid. However, searches for DC super ow and other super uid behavior were unsuccessful. We have studied another property which distinguishes solids from liquids — shear rigidity. The shear modulus of solid helium increases dramatically below 200 mK, with the same dependence on temperature, amplitude and 3He impurity concentration as the torsional oscillator frequency - the two phenomena are clearly related. However, the shear modulus changes are naturally explained in terms of dislocations moving in response to stress. The behavior of defects in solid helium is quite different from that in classical solids. We describe what we have learned about quantum "plasticity" in solid helium and how it may be related to the supersolid behavior seen in torsional oscillators.

Thèmes : Physique
Catégories: Colloquium / Séminaire général du département de physique
Mot-clés : mécanique des solides, fluide

Voir aussi

Auteur(s) John Beamish
University of Alberta, Canada - Department of physics
Professeur

Plus sur cet auteur
Voir la fiche de l'auteur

Cursus :

John Beamish began studying solid helium and dislocations as a graduate student at the University of Alberta, where he received his Ph.D. in 1982. His interest in quantum solids continued while he was a post-doctoral fellow at Brown University, a faculty member at the University of Delaware, and after he returned to the University of Alberta in 1991, where he is now a professor of physics. He also spent time as a visiting professor at the Pennsylvania State University and at Cornell University. In addition to supersolidity and quantum solids, his research interests include acoustics, freezing, and other phase transitions in confined liquids, superfluidity, and the low-temperature properties of aerogels and other porous glasses.

Cliquer ICI pour fermer Annexes Liens :
   - Solid Helium : Supersolidity or Quantum Plasticity ?

Téléchargements :
   - Télécharger la vidéo
   - Télécharger l'audio (mp3)

Dernière mise à jour : 05/12/2013

Liens utiles

Contact
Partenaires
Conditions d'utilisation
Mentions légales
Podcasts

CYCLES

> Colloquium DEC
> Les Ernest
> Les jeudis de l’archéologie
> Actualité critique
> Les jeudis de l’HPS
> Séminaire Médecine
   Humanités
> Journée Georges Bram
> Les lundis de la philo


> Les Nuits de l’ENS
> Semaine du cerveau
> Séminaire général du
   département d'informatique
> Séminaire général
   de physique
> Séminaire Transferts culturels
> La Voix d’un texte

PARTENARIATS

Louvre

France cuture

Institut Français

RESEAUX SOCIAUX

Retrouvez-nous sur Facebook

Twitter

Savoirs ENS
Tous droits réservés
@ 2011 ENS