Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session V1: New Developments in Supersolids |
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Sponsoring Units: DCMP Chair: William Halperin, Northwestern University Room: Colorado Convention Center Four Seasons 2-3 |
Thursday, March 8, 2007 11:15AM - 11:51AM |
V1.00001: Squeezing superfluid from a stone: Coupling superfluidity and elasticity in a supersolid Invited Speaker: Superfluidity---the ability of liquid $^4$He, when cooled below 2.176 K, to flow without resistance through narrow pores---has long served as a paradigm for the phenomenon of ``off-diagonal long-range order'' (ODLRO) in quantum liquids and superconductors. Supersolidity---the coexistence of ODLRO with the crystalline order of a solid---was proposed theoretically over 35 years ago as an even more exotic phase of solid $^4$He, but it has eluded detection. Recently, Kim and Chan [1,2] have reported an anomalous decoupling transition of solid $^4$He in a torsional oscillator measurement, and interpret their results as evidence for non-classical rotational inertia and a possible supersolid phase of $^4$He. In this talk I will give brief historical review of the theory of and experimental searches for supersolidity. I will then discuss a phenomenological Landau theory of the normal solid to supersolid (NS-SS) transition in which superfluidity is coupled to the elasticity of the crystalline $^4$He lattice, and underscore the implications of this theory for experimental searches for supersolidity [3]. I will also discuss a hydrodynamic model for supersolids, in which the additional broken gauge symmetry in the supersolid phase produces a collective mode that is analogous to second sound in superfluid helium. \newline \newline [1] E. Kim and M. H. W. Chan, Nature (London) \textbf{427}, 225 (2004). \newline [2] E. Kim and M. H. W. Chan, Science \textbf{305}, 1941 (2004). \newline [3] A. T. Dorsey, P. M. Goldbart, and J. Toner, ``Squeezing superfluid from a stone: Coupling superfluidity and elasticity in a supersolid,'' Phys. Rev. Lett. \textbf{96}, 055301 (2006). [Preview Abstract] |
Thursday, March 8, 2007 11:51AM - 12:27PM |
V1.00002: Elimination of the Supersolid State Through Crystal Annealing Invited Speaker: We have employed the torsional oscillator technique in the study of the supersolid state of solid 4He. We find that the supersolid state is not a universal property of solid helium, but in certain cases can be reduced or even eliminated through an annealing of the sample. We have also studied the supersolid in a number of cells with differing geometries, including cylindrical, cubic, and annular geometries, in an attempt to examine the possible influence of geometry on the stability of the supersolid state. [Preview Abstract] |
Thursday, March 8, 2007 12:27PM - 1:03PM |
V1.00003: Superfluidity of grain boundaries and supersolid behavior Invited Speaker: We have found that, at the liquid-solid equilibrium pressure $P_m$, supersolid behavior is due to the superfluidity of grain boundaries in solid helium [1]. After describing this experiment and reviewing some of the related theoretical work [2], we discuss the possibility that , at larger pressure ($P > P_m$), grain boundaries could also explain the supersolid behavior which was observed with torsional oscillators [3-6]. \newline \newline [1] S. Sasaki, R. Ishiguro, F. Caupin, H.J. Maris, and S. Balibar, Science 313, 1098 (2006)\newline [2] E. Burovski, E. Kozik, A. Kuklov, N. Prokof'ev, and B. Svistunov, Phys. Rev. Lett. 94, 165301 (2005)\newline [3] E. Kim and M.H. Chan, Nature 427, 225 (2004)\newline [4] E. Kim and M.H. Chan, Science 305, 1941 (2004)\newline [5] A.S.C. Rittner and J.D. Reppy, Phys. Rev. Lett. 97, 165301 (2006)\newline [6] K. Shirahama, Bull. Am. Phys. Soc. 51, 302 (2006) [Preview Abstract] |
Thursday, March 8, 2007 1:03PM - 1:39PM |
V1.00004: Supersolids? Invited Speaker: A brief, biased and selective review will be given of various theoretical and experimental results (recent and not so recent) addressing questions of supersolidity and related properties of quantum solids, especially helium. [Preview Abstract] |
Thursday, March 8, 2007 1:39PM - 2:15PM |
V1.00005: Measurements on the melting curve of $^{4}$He down to 10 mK Invited Speaker: Recent discovery of a nonclassical rotational inertia in solid $^{4}$He below about 0.2 K by Kim and Chan has initiated an intensive study on the properties of solid $^{4}$He. As Kim and Chan have interpreted their observation as the evidence of supersolid behavior, we have decided to measure very accurately the melting curve of $^{4}$He because, as the slope of the melting curve is proportional to the difference in the entropy of the liquid and solid phases, there should be an anomaly at the possible supersolid transition. We have measured the melting curve of $^{4}$He with the accuracy of about 0.5 microbar with $^{4}$He crystals which had various concentration of defects. All our samples showed only the expected $T^{4}$ dependence due to phonons without any sign of the supersolid transition in the temperature range of 80{\ldots}400 mK. Below 80 mK we observed a small deviation from $T^{4}$ dependence which, however, cannot be attributed to the supersolid transition because our recent measurements with the cell containing liquid sample only suggest that this deviation is by the temperature variation of properties of BeCu membrane of our capacitive pressure gauge. In addition to our published data with $^{4}$He of natural purity [Phys. Rev. Lett. 97, 165302 (2006)] we also report our recent measurements of the melting curve with ultra pure $^{4}$He (0.3 ppb of $^{3}$He impurities). In these measurements we followed optically the shape of the sample crystals which had very good quality. [Preview Abstract] |
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