Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session X8: The 50th Anniversary of the Prediction of Superfluidity of He3 |
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Sponsoring Units: FHP Chair: George Zimmerman, Boston University Room: Portland Ballroom 255 |
Thursday, March 18, 2010 2:30PM - 3:06PM |
X8.00001: Superconductivity with very repulsive interactions: He^3, Pierre Morel, and me Invited Speaker: |
Thursday, March 18, 2010 3:06PM - 3:42PM |
X8.00002: Early Thoughts on the Superfluidity of He$^{3}$ Invited Speaker: The history of the people and circumstances surrounding three papers will be presented. The first is the L.N. Cooper, R.L. Mills and A.M. Sessler, ``Possible Superfluidity of a System of Strongly Interacting Fermions'', Phys. Rev. \textbf{114}, 1377 (1959), in which the possibility of He$^{3}$ being a superfluid was suggested (although, it seemed not to be the case as only S-states were considered). The second is V.J. Emery and A.M. Sessler, ``Possible Phase Transition in Liquid He$^{3}$'', Phys. Rev. 119, 43 (1960) in which a definite prediction of superfluidity was proposed (in contrast with the conclusion of the earlier paper since here D-states were considered). And the third is A.E. Glassgold and A.M. Sessler, ``Flow Properties of Superfluid System of Fermions'', Il Nuovo Cimento Serie X, Vol 19, 723 (1960), in which the flow properties of superfluid He$^{3}$ were examined. Although the emphasis will be on the physicists, their background, educational experiences, and surroundings, some attention will be given to the physics in each of these papers for it was -- after all -- the physics that stimulated, along with the work of others, further theoretical work and, most importantly, the exceptional, and ultimately successful, experimental efforts of the following decade. [Preview Abstract] |
Thursday, March 18, 2010 3:42PM - 4:18PM |
X8.00003: Historically related puzzles in $^{3}$He: spin fluctuations, the specific heat, and the superfluid phase diagram Invited Speaker: By 1965 theorists agreed that the repulsive core of He-He interactions implied that BCS pairing in $^{3}$He could only occur with pair angular momentum l$>$ 0, and they had constructed the appropriate generalization of the BCS mean-field theory, including frameworks for including the quasiparticle interactions described by Landau's Fermi liquid theory. Between 1966 and the discovery of superfluid $^{3}$He in 1972, dramatic improvements in experimental technique revealed surprising non-analytic finite-temperature corrections to the Landau-theory specific heat. Another surprise appeared with the discovery of the superfluid phases, whose phase diagram was inconsistent with any plausible mean-field theory. Simple RPA-based spin-fluctuation models played a central historical role in the solution of both of these puzzles and in explaining the occurrence of spin-triplet $l $= 1 pairing, but the corrections to the Landau and BCS molecular field theories first identified in paramagnon models have turned out to be general properties of Fermi liquids, and the Landau and BCS molecular fields now appear not to be dominated by spin fluctuations. [Preview Abstract] |
Thursday, March 18, 2010 4:18PM - 4:54PM |
X8.00004: Early Days of Superfluid $^{3}$He: An Experimenter's View Invited Speaker: The formulation of the BCS theory led theorists to investigate possible non-S-wave pairing in liquid $^{3}$He. Unfortunately as time went on, estimates for the pairing temperature became unattainably low. Nevertheless, the push to lower temperatures by experimentalists continued and was facilitated by the invention of the dilution refrigerator. Nuclear adiabatic demagnetization could then be used to cool liquid $^{3}$He to $\sim $1 mK as demonstrated by Goodkind. An alternate approach, suggested by Pomeranchuk, involved adiabatic compression of liquid $^{3}$He into the solid phase. Efforts to develop this technique at the Kapitza Institute, La Jolla and Cornell achieved success in demonstrating cooling of mixtures of liquid and solid $^{3}$He to $\sim $ 1 mK following dilution refrigerator pre-cooling. Although there was great pessimism regarding the possible observation of pairing in liquid $^{3}$He, the unsettled problem of magnetic ordering in solid $^{3}$He beckoned. Ultimately two phase transition along the melting curve were observed by Osheroff \underline {et} \underline {al} at Cornell. Although first associated with solid $^{3}$He, extensive NMR studies showed them to be two new phases of liquid $^{3}$He. A brief history of experiments at various laboratories following the discovery is given, along with early interpretations given by Anderson and Morel and Balian and Werthamer. The key role of Leggett's spin dynamics is also discussed. [Preview Abstract] |
Thursday, March 18, 2010 4:54PM - 5:30PM |
X8.00005: Superfluid 3-He:understanding the experiments Invited Speaker: When the first experiments which gave evidence for anomalous behavior in liquid 3-He below 3 mK came out in the spring and summer of 1972,it appeared difficult to fit them into the framework of the pre-existing theory of the superfluid phase-so much so that not everyone was immediately convinced that what was being seen was indeed ``superfluid 3-He.'' In the first place,it was clear that there was not one but two (and eventually three) new phases,and secondly,the anomalies in the NMR behavior which were one of the most spectacular signatures of the new phases had not been anticipated.I will review how over the next year or so we reached a picture of the new phases which was consistent both with pre-1972 theoretical ideas and with the experiments. [Preview Abstract] |
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