${}^4$He Crystal Quality and Rotational Response in a Transparent Torsional Oscillator

Abstract

We have studied natural purity ${}^4$He single crystals and polycrystals between 10 and 600 mK using a torsional oscillator with a 2 cm${}^3$ rigid cell made of sapphire with a smooth geometry. As the temperature was lowered, we observed sample dependent but reproducible resonant frequency shifts that could be attributed to a supersolid fraction of order 0.1%. However, these shifts were observed with single crystals, not with polycrystals. Our results indicate that, in our case, the rotational anomaly of solid helium is more likely due to a change in stiffness than to supersolidity. This interpretation would presumably require gliding of dislocations in more directions than previously thought.

References in corpus (7)

• Low Temperature Shear Modulus Changes in Solid 4-He and Connection to Supersolidity
• Annealing Effect for Supersolid Fraction in ${}^4$He
• Nonclassical Rotational Inertia in Single Crystal Helium
• A non-superfluid origin of the non-classical rotational inertia in a bulk sample of solid 4He
• Thermal History of Solid 4He Under Oscillation
• Low frequency acoustics in solid ${}^4$He at low temperature
• The glassy response of solid He-4 to torsional oscillations

Cited by in corpus (9)

• Absence of supersolidity in solid helium in porous Vycor glass
• Upper limit of supersoldity in solid helium
• Dislocation induced anomalous softening of solid helium
• The low temperature elastic anomalies in solid helium
• Plastic response by dislocation glide in solid helium under dc strain rate loading
• Frequency-dependent Study of Solid Helium-4 Contained in a Rigid Double-torus Torsional Oscillator
• Excitations of amorphous solid helium
• Superfluid transition in a correlated defect network
• Saga of Superfluid Solids