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Abstracts
P2.23
Superfluid-like Responses in Rotating Solid Helium
Jaewon Choi(1), Tomoya Tsuiki(2,3), Daisuke Takahashi(4), Kimitoshi Kono(3),
Keiya Shirahama(2), Hyoungsoon Choi(1), Eunseong Kim(1)
1) Department of Physics and Center for Supersolid and Quantum Matter
Research, Korea advanced Institute of Science and Technology (KAIST), 291
Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
2) Department of Physics, Keio University, 3-14-1 Hiyoshi, Yokohama-shi,
Kanagawa 223-8522, Japan
3) Quantum Condensed Phase Research Team, Center for Emergent Materials
Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
4) Division of General Education, Ashikaga Institute of Technology, 268-1
Omae-cho, Ashikaga, Tochigi 326-8558, Japan
The influence of DC rotation to a torsional oscillator (TO) cannot be clearly
understood within the framework of elastic stiffening of solid helium since no effect
is observed in the shear modulus measurements. In this study, we re-investigated
the rotation effect on solid helium by using a rigid double-torus TO. Although new
rigid TO experiments failed to reproduce the substantial DC rotation effect, an
extremely small suppression of a frequency-independent period drop as small as
1.8 ppm was observed with rotation speed of 4rad/s. The signal is distinguishable
from the frequency-dependent elastic contribution in various aspects. To elucidate
its origin, several possibilities will be discussed.
P2.24
Friction in solid
4
He, classical and quantum
Almog Danzig(1), Ori Scaly(1), and Emil Polturak(1)
1) Physics Department, Technion- Israel Institute of Technology, Haifa 32000,
Israel
“Macroscopic quantum friction” describes an irreversible exchange of quantized
excitations between two bodies in relative motion. In usual materials and at high
temperatures, quantum friction is negligible compared with classical friction,
namely plastic deformation of the interface. In contrast, in solid He the measured
classical friction is many orders of magnitude lower[1]. This opens the way to
detect quantum friction, which in solid He is mediated by irreversible exchange of
phonons[2]. While the phonon mechanism of quantum friction seems understood,
it is the unusually low classical friction in solid He which remains a puzzle. This
low friction alludes to some mass transport mechanisms unique to solid He, which
at low temperatures allows plastic deformation with little or no dissipation.
1. A. Eyal, E. Livne, and E. Polturak, J Low Temp. Phys. DOI
10.1007/s10909-016-1495-y
2. V.L. Popov, Phys. Rev. Lett. 83, 1632, (1999).
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