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Baddar, H.; Ahlers, Guenter; Kuehn, Kerry; Fu, Haiying

doi:10.1023/a:1004683717235

Cited by 12 publications

(4 citation statements)

References 24 publications

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“…If the resistance is large enough, the SOC state can self organize on the changing mutual friction thermal resistance instead of the crossover from superfluid to normal fluid flow. Baddar et al measured the resistance due to mutual friction to be R = (t/(Q/393 W/cm 2 ) 0.904 ) −2.8 [23]. Using our value for t SOC (Q) = (Q/767) 0.813 , we find that mutual friction gives a gradient of 1.273 µK/cm for t SOC (Q) at Q = 20 µW/cm 2 .…”

Section: T Soc Vs Q and Finding T λmentioning

confidence: 48%

Experiments on the Self-Organized Critical State of 4He

Chatto

Lee

Duncan³

et al. 2007

J Low Temp Phys

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AcknowledgementsThere are a number of people I would like to thank for their contributions to this thesis. My advisor David Goodstein was insightful, encouraging, and patient throughout the many challenges of performing a low-temperature experiment. Our conversations were always helpful because David has an extraordinary ability to make complicated concepts seem simple and intuitive. I had two mentors in the lab, Peter Day and Richard Lee, who taught me everything I know about performing experiments in low-temperature physics. My first lab experience was working with Peter. He provided me with the cryostat I used throughout my graduate career, answered hundreds of questions, and patiently showed me the techniques I needed. Richard returned to Caltech as my thesis experiment was taking shape. He was also an excellent resource for the tricks and techniques of low-temperature physics. (Plus, he made B.O.B.2, the electrical filtering system on this cryostat). However, what helped me most was that he patiently asked hundreds of questions, which forced me to think through all the details of my experiment. It is with his help that I avoided many pitfalls.There are a number of other physicists who made significant contributions to this work. Particularly helpful were the members of the DYNAMX team from the University of New Mexico (Rob Duncan, Dimitri Sergatskov, Alex Babkin, and Steve Boyd). They provided material help with the cryo-valve system and the construction of the experimental cell. In addition, they provided a lot of expertise on performing experiments on the SOC state of 4 He. In particular, I would like to thank Rob Duncan, who served as a secondary thesis advisor during a critical time in the experiment as David Goodstein recovered from an injury. Also helpful were discussions with two theorists, Peter Weichman and Rudolf Haussmann, who helped give meaning to my results.I would like to thank my parents for many many years of encouragement and support, and not asking me too often when I was going to get my degree.I would also like to thank my wife Avital, who provided an enormous amount of support and, through an intricate dance of prodding and patience, helped guide me through this endeavor. Lastly, I thank my son Jacob, whose arrival helped destroy the illusion that maybe, just maybe, I could be a graduate student forever. We report the first results of the heat capacity of the SOC state, C ∇T , for heat fluxes 60nW/cm 2 < Q < 13 µW/cm 2 and corresponding temperatures 9 nK > T SOC − T λ > −1.1 µK. We find that C ∇T tracks the static (i.e., zero heat flux) unrounded (i.e., in zero gravity) heat capacity C 0 with two exceptions. The first is that within 250 nK of T λ , C ∇T is depressed relative to C 0 and the maximum in C ∇T is shifted to 50 nK below T λ . The second difference is that at high heat flux, C ∇T is again depressed relative to C 0 with the departure starting at about 650 nK below T λ .We present the most extensive measurements of the speed and attenuation of the SOC wave to date. We report wav...

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Section: T Soc Vs Q and Finding T λmentioning

confidence: 48%

Experiments on the Self-Organized Critical State of 4He

Chatto

Lee

Duncan³

et al. 2007

J Low Temp Phys

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“…In Fig. 3 of our previous paper [14] we have compared the result of our second-type solution with experimental data by Baddar et al [32]. The experimental thermal resistivity is lower by a factor of 20 than our theoretical result.…”

Section: Discussionmentioning

confidence: 57%

Renormalization-group calculation of the superfluid/normal-fluid interface of liquid4He in gravity nearTλ

Haussmann

2012

Phys. Rev. B

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The superfluid/normal-fluid interface of liquid 4 He is investigated in gravity on earth where a small heat current Q flows vertically upward or downward. We present a local space-and time-dependent renormalization-group (RG) calculation based on model F which describes the dynamic critical effects for temperatures T near the superfluid transition T λ . The model-F equations are rewritten in a dimensionless renormalized form and solved numerically as partial differential equations. Perturbative corrections are included for the spatially inhomogeneous system within a self-consistent one-loop approximation. The RG flow parameter is determined locally as a function of space and time by a constraint equation which is solved by a Newton iteration. As a result we obtain the temperature profile of the interface. Furthermore we calculate the average order parameter ψ , the correlation length ξ, the specific heat CQ and the thermal resistivity ρT where we observe a rounding of the critical singularity by the gravity and the heat current. We compare the thermal resistivity with an experiment and find good qualitative agreement. Moreover we discuss our previous approach for larger heat currents and the self-organized critical state and show that our theory agrees with recent experiments in this latter regime.

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“…We are dealing with a similar situation arising due to the nonuniform cooling as the critical temperature in the superfluid nucleus is approached. The results of numerical calculation [23] and experimental data [24], [25] indicate the formation of a "vortex" superfluid phase with a higher but finite thermal conductivity without a superfluid transport. The mechanism of vortex formation and the vortex phase of this kind have been poorly studied both theoretically and experimentally.…”

Section: The Later Stage Of Instanton Growthmentioning

confidence: 99%

Condensation and vortex formation in a Bose gas upon cooling

Brener

Iordanskiy²,

Saptsov³

2006

Phys. Rev. E

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The mechanism for the transition of a Bose gas to the superfluid state via thermal fluctuations is considered. It is shown that in the process of external cooling some critical fluctuations ͑instantons͒ are formed above the critical temperature. The probability of the instanton formation is calculated in the three-and two-dimensional cases. It is found that this probability increases as the system approaches the transition temperature. It is shown that the evolution of an individual instanton is impossible without the formation of vortices in its superfluid part.

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Cited by 12 publications

References 24 publications

Experiments on the Self-Organized Critical State of 4He

Experiments on the Self-Organized Critical State of 4He

Renormalization-group calculation of the superfluid/normal-fluid interface of liquid4He in gravity nearTλ

Condensation and vortex formation in a Bose gas upon cooling

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