QFS2016 Book of Abstracts

Abstracts

P3.24 Circulation and Vortices in Rotating Superfluid Helium 4 Confined in a Ring Makiuchi, T.(1), Murakawa, S.(2), Shirahama K.(1) (1) Keio University, Faculty of Science and Technology, Department of Physics, Yokohama, 223-8522, Japan (2) University of Tokyo, Cryogenics Research Center, Bunkyo, 113-0032, Japan We investigated the circulation and quantum vortices in a rotating superfluid 4 He confined in a ring. A torsional oscillator with a torus cavity and a superleak separation was used to produce and to detect a standing wave of second sound in circumferential direction. It is known that the second sound velocity is decreased in the presence of vortices due to the mutual friction (Miller et al., PRB, 17 1035 (1978)). We observed a hysteresis in second sound velocity versus rotation angular velocity from 0 to 2.5 rad/s. This implies vortices are (meta-)stable even at zero angular velocity for a couple of days. An analogy to type-II superconductors and a stability of vortices are discussed. P3.25 Theoretical analysis for mobility of ions below a free surface of 3 He-B Yasumasa Tsutsumi Department of Basic Science, The University of Tokyo At a surface of the superfluid 3 He-B, Majorana fermions emerge as the surface bound state. Observation of the surface bound state was attempted via mobility of ions below a free surface [1]. Although the observed mobility is suppressed than that in the bulk B-phase at low temperatures, it is independent of the trapped depth which is shorter than the coherence length. Then, it has not been clear whether the experiment could observe the surface bound state. In this presentation, I will show that the mobility of ions below a free surface, at which quasiparticles are specularly reflected, does not so much depend on the depth within the coherence length. Therefore, I conclude that the experiment observed the ideal surface bound state with linear dispersion. [1] H. Ikegami et al., J. Phys. Soc. Jpn. 82, 124607 (2013).

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