QFS2016 Book of Abstracts

Abstracts

I2.3 Mass flow through thin solid helium samples* Shin, Jae-ho(1); Kim, DukYoung(2); Haziot, Ariel(3); Chan, M.H.W.(4) 1) Penn State University, PA USA 2) Penn State University, PA, USA; current address: Los Alamos Nat. Lab. 3) Penn State University, PA, USA; current address: Neel Insitut, France 4) Penn State University, PA, USA We will report measurements of superfluid-like mass flow through solid helium samples sandwiched between two superfluid reservoirs as used sby Hallock at the Univ.of Mass.( PRL 100, 235301, 2008). Instead of a solid sample of 4 cm as employed by Hallock, our solid samples have thicknesses of 8, 50 and 1000 microns. Our measurements show interesting differences from that found at UMass, flow rate as a function of path length, temperature and pressure will be presented. Work supported by US NSF. O2.2 Defect motions in quantum solids with spins Cheng Zhi-Gang, Beamish John Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1 Canada Defect motion in solid helium has uniquely quantum nature due to the large zero-point motion of helium atoms. Dislocations in solid 4 He are strongly pinned by 3 He impurities at low temperature but extremely mobile at high temperature, causing the shear modulus greatly reduced. 3 He has even larger zero-point motion than 4 He and extra nuclear spins, which may govern defect motion differently. We report shear modulus measurements of hcp solid 3 He to explore its dislocation motion. We observed the crossover between stiff and soft states due to 4 He impurities immobilizing dislocations as static pinning sites, as well as dissipation strongly depending on frequency. Both suggest the coupling between spin system and dislocation motion. We also observed extra softening at high temperature that does not exist for solid 4 He.

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