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Experiments on the Self-Organized Critical State of ^4He

Chatto, A. R. and Lee, R. A. M. and Duncan, R. V. and Goodstein, D. L. (2007) Experiments on the Self-Organized Critical State of ^4He. Journal of Low Temperature Physics, 148 (5-6). pp. 519-526. ISSN 0022-2291. doi:10.1007/s10909-007-9484-9. https://resolver.caltech.edu/CaltechAUTHORS:20151216-095247690

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Abstract

When a heat flux Q is applied downward through a sample of ^4He near the lambda transition, the helium self organizes such that the gradient in temperature matches the gravity-induced gradient in T_λ. All the helium in the sample is then at the same reduced temperature ϵ=T−T_λ_T_λ and the helium is said to be in the Self-Organized Critical (SOC) state. We have made the first measurements of the ^4He SOC state specific heat, C_(∇T) (T(Q)). There is no measurable difference between C_(∇T) and the static zero-gravity 4He specific heat for temperatures between 650 and 250 nK below T_λ. Closer to T_λ , the specific heat is depressed and reaches a maximum value at 50 nK below T_λ. This depression is similar to that predicted theoretically as reported by R. Haussmann (Phys. Rev. B 60, 12349, 1999). Contrary to the expectations of theory, however, we see another depression far below T_λ. In addition, over the heat flux range of 30 nW/cm^2 to 13 μW/cm^2, we have made improved measurements of the speed of a recently discovered propagating thermal mode, which travels only upstream against the nominal heat flux of the SOC state. We are able to accurately predict the speed of this wave by treating the helium of SOC state as a traditional fluid with a temperature dependent thermal conductivity.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1007/s10909-007-9484-9DOIArticle
http://link.springer.com/article/10.1007/s10909-007-9484-9PublisherArticle
http://rdcu.be/vM7APublisherFree ReadCube access
ORCID:
AuthorORCID
Lee, R. A. M.0000-0001-6509-697X
Additional Information:© 2007 Springer Science+Business Media, LLC. First online: 30 May 2007. We would like to thank Peter Day for his helpful advice and his assistance with developing the cryostat and experimental platform. We would also like to thank Dmitri Sergatskov, Steve Boyd, Alex Babkin, Alexander Churilov, and Talso Chui for helpful discussions and assistance with cell construction and cryovalve assembly and operation. This work was supported in part by the Fundamental Physics’ Discipline of the Microgravity Science Office of NASA.
Funders:
Funding AgencyGrant Number
NASAUNSPECIFIED
Issue or Number:5-6
Classification Code:PACS 67.40.Pm · 05.65.+b · 05.70.Jk
DOI:10.1007/s10909-007-9484-9
Record Number:CaltechAUTHORS:20151216-095247690
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20151216-095247690
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:62965
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:16 Dec 2015 19:44
Last Modified:10 Nov 2021 23:09

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