QFS2016 Book of Abstracts

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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