Nonclassical Rotational Inertia in Helium Crystals

Clark, Anthony C.; West, Joshua T.; Chan, Moses H. W.

doi:10.1103/physrevlett.99.135302

Cited by 107 publications

(179 citation statements)

References 39 publications

Supporting

Mentioning

167

Contrasting

Order By: Relevance

“…Recent successive TO experiments [7,8,9,10,11,12] confirmed the finding of the anomalous behavior. In addition, hysteresis behavior and long equilibration times have been observed [9,12,13], which depend strongly on growth history and annealing [7].…”

Section: Introductionsupporting

confidence: 59%

A Glassy Contribution to the Heat Capacity of hcp 4He Solids

Graf

Balatsky

2010

J Low Temp Phys

View full text Add to dashboard Cite

We model the low-temperature specific heat of solid 4 He in the hexagonal closed packed structure by invoking two-level tunneling states in addition to the usual phonon contribution of a Debye crystal for temperatures far below the Debye temperature, T < Θ D /50. By introducing a cutoff energy in the two-level tunneling density of states, we can describe the excess specific heat observed in solid hcp 4 He, as well as the low-temperature linear term in the specific heat. Agreement is found with recent measurements of the temperature behavior of both specific heat and pressure. These results suggest the presence of a very small fraction, at the parts-per-million (ppm) level, of two-level tunneling systems in solid 4 He, irrespective of the existence of supersolidity.

show abstract

Section: Introductionsupporting

confidence: 59%

A Glassy Contribution to the Heat Capacity of hcp 4He Solids

Graf

Balatsky

2010

J Low Temp Phys

View full text Add to dashboard Cite

show abstract

“…In the low temperature experiments the crystals were grown using a blocked capillary method which results in polycrystalline samples 26 , with the exception of one experiment 27 , in which the cell contained sharp corners, which again makes it impossible to fill it with a single crystal.…”

Section: Discussionmentioning

confidence: 99%

BCC vs. HCP—The Effect of Crystal Symmetry on the High Temperature Mobility of Solid 4He

Eyal

Polturak²

2012

J Low Temp Phys

View full text Add to dashboard Cite

We report results of torsional oscillator (TO) experiments on solid 4 He at temperatures above 1K. We have previously found that single crystals, once disordered, show some mobility (decoupled mass) even at these rather high temperatures. The decoupled mass fraction with single crystals is typically 20-30%. In the present work we performed similar measurements on polycrystalline solid samples. The decoupled mass with polycrystals is much smaller, ∼ 1%, similar to what is observed by other groups. In particular, we compared the properties of samples grown with the TO's rotation axis at different orientations with respect to gravity. We found that the decoupled mass fraction of bcc samples is independent of the angle between the rotation axis and gravity. In contrast, hcp samples showed a significant difference in the fraction of decoupled mass as the angle between the rotation axis and gravity was varied between zero and 85 degrees. Dislocation dynamics in the solid offers one possible explanation of this anisotropy.

show abstract

“…It would be surprising if such a small concentration of binding sites x d could have a measurable effect on T 1 . However, there are other indications that the density of dislocations or other defects must be much larger than the estimate quoted above, if the NCRIF observations are explained either by superflow along dislocations cores [23] or as a direct mechanical effect unconnected with supersolidity [24]. Figure 4 shows the temperature dependence of T 1 along with the occupation probability for 3 He binding sites and another model discussed below.…”

mentioning

confidence: 97%