QFS2016 Book of Abstracts

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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 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 4He are strongly pinned
by 3He 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 4He
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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