Characterization of the Surface of Moving solid 4He

Abstract

Crystal grains of solid ${}^4$He can move in relation to each other even when embedded inside the solid. In this work, we characterize a macroscopic motion of solid hcp ${}^4$He composed of such grains. Motion is induced by applying an external torque to the solid contained inside an annular channel mounted on a torsional oscillator. In order to characterize the surface of the moving solid, we developed an in-situ flow detection method using a sensitive "microphone" embedded in the wall of the channel. Motion is detected by counting the vibrations induced by rows of He atoms moving past the microphone. Such vibrations were detected only at T=0.5K, our lowest temperature. At this temperature, the measured dissipation associated with the solid He is zero within our accuracy. Our results indicate that the orientation of the surface of the moving solid is the (0001) basal plane of the hcp structure. At T=0.5 K, we found that for speeds < 7 micrometer/sec, the solid flows without detectable friction.

arXiv comment17 pages, 9 figures

References in corpus (10)

• Low Temperature Shear Modulus Changes in Solid 4-He and Connection to Supersolidity
• Absence of supersolidity in solid helium in porous Vycor glass
• Superfluidity of Grain Boundaries in Solid Helium-4
• The giant plasticity of a quantum crystal
• Thermal History of Solid 4He Under Oscillation
• Critical dislocation speed in helium-4 crystals
• Evidence for a High-Temperature Disorder-Induced Mobility in Solid ${}^4$He
• Observation of Macroscopic Structural Fluctuations in bcc Solid 4He
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• BCC vs. HCP - The Effect of Crystal Symmetry on the High Temperature Mobility of Solid ${}^4$He

Cited by in corpus (1)

• Mass Superflux in Solid Helium: the Role of ${}^3$He Impurities