Critical behavior of superfluid {sup 4}He films adsorbed in aerogel glass
- Laboratory of Atomic and Solid State Physics and Materials Science Center, Clark Hall, Cornell University, Ithaca, New York 14853-2501 (United States)
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)
- Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)
We present measurements of the superfluid density and heat capacity of thin films of {sup 4}He adsorbed in aerogel glass. We find that the critical behavior of the superfluid density for films with transition temperatures between 50 mK and 1 K is similar to that seen for films adsorbed on Vycor. Power-law behavior is observed over at least one order of magnitude in reduced temperature with an exponent {zeta}=0.63{plus_minus}0.03. This exponent is much smaller than the value 0.811{plus_minus}0.004 found when the pores were filled with helium. We also find that the exponent is unchanged by the addition of small amounts of {sup 3}He. These results are consistent with the existence of a correlation length that diverges at the superfluid transition. Unlike for full-pore {sup 4}He aerogel, the correlation length is long compared with all structural length scales throughout the superfluid density power-law regime, thus leading to the more bulklike critical behavior. The heat capacity of {sup 4}He films in aerogel shows no singularity like that seen for full-pore {sup 4}He aerogel or for thin films adsorbed in Vycor. We show that this result is consistent with the predictions of hyperuniversality given the long correlation lengths implied by the superfluid density measurements.
- OSTI ID:
- 44578
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 18 Vol. 51; ISSN PRBMDO; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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