Shear modulus of solid 4He confined in aerogel

• Author / Creator

  Rabbani, Arif

• Torsional oscillator experiments on solid 4He show supersolid behavior which appears to be associated with disorder. However, confining helium in the pores of an aerogel does not enhance the supersolid decoupling, even though x-ray measurements confirm that the crystals are highly disordered. Solid helium’s shear modulus also shows anomalous behavior below 150 mK, stiffening as mobile dislocations are pinned by 3He impurities at low temperatures. A highly porous material should also provide effective pinning sites for dislocations. We have made shear modulus measurements on solid 4He grown in a 95% porosity aerogel. We see large modulus decreases as the samples are warmed but at much higher temperatures and over a broader range than in bulk 4He. The frequency dependence of the modulus and dissipation are consistent with a thermally activated process. The activation energies are roughly 10 to 15 K and may be associated with vacancy motion.

• Subjects / Keywords

  • Aerogels
  • Order-disorder models
  • Superfluidity
  • Solid helium
  • Solid helium--Density--Measurement

• Graduation date

  Spring 2011

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R34G9B

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.