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Abstract
Using a novel SQUIDbased torsional oscillator (TO) technique to achieve increased sensitivity and dynamic range, we studied TO's containing solid He4. Below similar to 250 mK, the TO resonance frequency f increases and its dissipation D passes through a maximum as first reported by Kim and Chan. To achieve unbiased analysis of such He4 rotational dynamics, we implemented a new approach based upon the generalized rotational susceptibility . Upon cooling, we found that equilibration times within f(T) and D(T) exhibit a complex synchronized ultraslow evolution toward equilibrium indicative of glassy freezing of crystal disorder conformations which strongly influence the rotational dynamics. We explored a more specific with tau(T) representing a relaxation rate for inertially active microscopic excitations. In such models, the characteristic temperature T (au) at which df/dT and D pass simultaneously through a maximum occurs when the TO angular frequency omega and the relaxation rate are matched: omega I"(T (au))=1. Then, by introducing the free inertial decay (FID) technique to solid He4 TO studies, we carried out a comprehensive map of f(T,V) and D(T,V) where V is the maximum TO rim velocity. These data indicated that the same microscopic excitations controlling the TO motions are generated independently by thermal and mechanical stimulation of the crystal. Moreover, a measure for their relaxation times tau(T,V) diverges smoothly everywhere without exhibiting a critical temperature or velocity, as expected in omega I"=1 models. Finally, following the observations of Day and Beamish, we showed that the combined temperaturevelocity dependence of the TO response is indistinguishable from the combined temperaturestrain dependence of the He4 shear modulus. Together, these observations imply that ultraslow equilibration of crystal disorder conformations controls the rotational dynamics and, for any given disorder conformation, the anomalous rotational responses of solid He4 are associated with generation of the same microscopic excitations as those produced by direct shear strain.
Original language  English 

Pages (fromto)  180196 
Number of pages  17 
Journal  Journal of Low Temperature Physics 
Volume  169 
Issue number  34 
DOIs  
Publication status  Published  Nov 2012 
Keywords
 Supersolid helium
 Generalized rotational susceptibility
 Superglass
 Torsional oscillator
 BOSEEINSTEIN CONDENSATION
 SUPERSOLID HE4
 SUPERFLUID
 TRANSITION
 OSCILLATIONS
 CRYSTALS
 DYNAMICS
 HELIUM
 PHASE
 FILMS
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Dive into the research topics of 'Generalized Rotational Susceptibility Studies of Solid He4'. Together they form a unique fingerprint.Projects
 1 Finished

Topological Protection and NonEquilibriu: Topological Protection and NonEquilibrium States in Strongly Correlated Electron Systems
Wahl, P., Baumberger, F., Davis, J. C., Green, A., Hooley, C., Keeling, J. M. J. & Mackenzie, A.
1/09/11 → 31/08/17
Project: Standard