Search for fourth sound propagation in supersolid He4

Aoki, Yuki; Kojima, H.; Lin, Xi

doi:10.1063/1.2911651

Cited by 16 publications

(12 citation statements)

References 52 publications

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“…Propagation of fourth sound that would be expected for a superfluid has not been detected. 17,18 The shear modulus of a thin solid 4 He slab was found 13 to "stiffen" in a very similar manner as the frequency of TO containing an annular solid 4 He sample was found 1 to increase with decreasing temperature. This similarity indicated a common origin of these two effects.…”

Section: Introductionmentioning

confidence: 78%

Effects ofHe3impurity on solidHe4studied by compo

et al. 2011

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Frequency shifts and dissipation of a compound torsional oscillator induced by solid 4 He samples containing 3 He impurity concentrations (x3 = 0.3, 3, 6, 12 and 25 in units of 10 −6 ) have been measured at two resonant mode frequencies (f1 = 493 and f2 = 1164 Hz) at temperatures (T ) between 0.02 and 1.1 K. The fractional frequency shifts of the f1 mode were much smaller than those of the f2 mode. The observed frequency shifts continued to decrease as T was increased above 0.3 K, and the conventional non-classical rotation inertia fraction was not well defined in all samples with x3 ≥ 3 ppm. Temperatures where peaks in dissipation of the f2 mode occurred were higher than those of the f1 mode in all samples. The peak dissipation magnitudes of the f1 mode was greater than those of the f2 mode in all samples. The activation energy and the characteristic time (τ0) were extracted for each sample from an Arrhenius plot between mode frequencies and inverse peak temperatures. The average activation energy among all samples was 430 mK, and τ0 ranged from 2×10 −7 s to 5×10 −5 s in samples with x3 = 0.3 to 25 ppm. The characteristic time increased with increasing x3. Observed temperature dependence of dissipation were consistent with those expected from a simple Debye relaxation model if the dissipation peak magnitude was separately adjusted for each mode. Observed frequency shifts were greater than those expected from the model. The discrepancies between the observed and the model frequency shifts increased at the higher frequency mode.

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Section: Introductionmentioning

confidence: 78%

Effects ofHe3impurity on solidHe4studied by compo

et al. 2011

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“…Neither a fourth sound mode nor velocity shifts have been observed. [17][18][19] However, a stiffened shear response is observed, 20,21 although not enough to explain the observed NCRI. 16 Note also recent work indicating that supersolidity in 4 He can only occur below 55 mK.…”

Section: Introductionmentioning

confidence: 95%

Generation efficiencies for propagating modes in a supersolid

Sears¹,

Saslow²

2010

Phys. Rev. B

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Using Andreev and Lifshitz's supersolid hydrodynamics, we obtain the propagating longitudinal modes at nonzero applied pressure P a ͑necessary for solid 4 He͒, and their generation efficiencies by heaters and transducers. For small P a , a solid develops an internal pressure P ϳ P a 2 . This theory has stress contributions both from the lattice and an internal pressure P. Because both types of stress are included, the normal-mode analysis differs from previous works. Not surprisingly, transducers are significantly more efficient at producing elastic waves and heaters are significantly more efficient at producing fourth sound waves. We take the system to be isotropic, which should apply to systems that are glassy or consist of many crystallites; the results should also apply, at least qualitatively, to single-crystal hcp 4 He.scribe a supersolid related to the NCRI effect proposed by Leggett than to vacancy superflow. Most of the present work assumes that the system is isotropic. One effect this has is that the superfluid density, which properly is a second-rank tensor s J , is proportional to the unit matrix so we take s J Ϸ 1 J s . 23,24 We then write the superfluid fraction as

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“…In a recent attempt to find such an effect, Kim and Chan measured the resonant period of a torsional oscillator (TO) containing solid helium and found an intriguing phenomenon: a fraction of solid helium apparently decoupled from oscillating bodies marked by the reduction of the resonant period [14,15]. This was interpreted as the nonclassical rotational inertia (NCRI) [4] of solid helium.Despite the initial excitement of the possible discovery of a supersolid, it turned out to be rather difficult to replicate the intrinsic characteristics of superfluids with solid 4 He [16][17][18][19][20][21]. An interesting development in the field came from a somewhat unexpected front of measuring the shear modulus of the solid.…”

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confidence: 99%

“…Despite the initial excitement of the possible discovery of a supersolid, it turned out to be rather difficult to replicate the intrinsic characteristics of superfluids with solid 4 He [16][17][18][19][20][21]. An interesting development in the field came from a somewhat unexpected front of measuring the shear modulus of the solid.…”

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confidence: 99%

Staircaselike Suppression of Supersolidity under Rotation

et al. 2012

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There are a number of distinct signatures of superfluids, one of which is the appearance of quantized vortices. There have been some attempts to understand the putative supersolid 4He in the vortex framework, but no conclusive evidence that supports the existence of the vortices has been reported. Here, we investigate the rotation velocity dependence of the torsional oscillation of solid 4He at various temperatures. The velocity sweep reveals intriguing periodic staircaselike features below about 300 mK. The staircase patterns show remarkable periodicity, and we interpret these patterns as a consequence of vortex injection. However, there are some features that cannot be accounted for with simple injection of vortices into superfluid, and further investigation is required.

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Search for fourth sound propagation in supersolid He4

Cited by 16 publications

References 52 publications

Effects ofHe3impurity on solidHe4studied by compo

Effects ofHe3impurity on solidHe4studied by compo

Generation efficiencies for propagating modes in a supersolid

Staircaselike Suppression of Supersolidity under Rotation

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