Nucleation of crystals and superfluid droplets in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">He</mml:mi><mml:mprescripts /><mml:none /><mml:mn>4</mml:mn></mml:mmultiscripts></mml:math>induced by acoustic waves

Abe, Haruka; Ogasawara, F.; Saitoh, Y.; Tatara, Tsuneo; Nomura, R.; Okuda, Y.

doi:10.1103/physrevb.71.214506

Cited by 15 publications

(10 citation statements)

References 20 publications

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“…In the metastable superfluid at a few millibar above the melting pressure, an acoustic wave pulse was applied by the upper transducer to initiate nucleation of a hexagonal-closed-packed (hcp) 4 He seed crystal on the transducer surface [13,21,30]. The crystal eventually fell in the superfluid and landed on the bottom.…”

Section: Methodsmentioning

confidence: 99%

Asymmetry in melting and growth relaxation of⁴He crystals in superfluid after manipulation by acoustic radiation pressure

Nomura

Abe²,

Okuda

2017

New J. Phys.

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The relaxation dynamics of the crystal-superfluid interface of 4 He after deformation induced by acoustic radiation pressure was investigated for various crystal orientations. The melting relaxation after growth was approximately 10 times slower than the growth relaxation after melting for vicinal surfaces and facets, while both relaxation times were consistent with each other for rough surfaces. The asymmetry in the time constant between the melting and growth of vicinal surfaces and facets can be qualitatively explained as the effect of superflow induced by local rapid interface motion, such as a quick rounding of facet edges of the 4 He crystal. Rough surfaces move more isotropically and no significant local rapid interface motion is induced; therefore, their relaxation is likely to be symmetric with a minimal effect of superflow. While the growth relaxation was simply back to the initial shape in a single stage, the melting relaxation was much more complex with multiple stages and the exhibition of various anomalous shapes depending on temperature. Anomalous shapes such as needle-like shapes during melting have a larger curvature and higher energy and thus should have disappeared more quickly than the growth shape with a smaller curvature, but they were considerably stable and disappeared slowly. This counter-intuitive asymmetry suggests the significant role of superflow in the relaxation process. 4 He quantum crystals in superfluid is the exceptional material to be manipulated by small driving forces such as heat, gravity, and flow [6-13], because they grow extremely fast at low temperatures and play a very important role in understanding the fundamental aspects of crystal growth physics [14][15][16][17]. In previous reports, we have demonstrated that acoustic radiation pressure, which is the small second-order acoustic force usually not relevant to the crystallization process [18,19], induces both growth and melting of 4 He crystals and is a very useful tool to manipulate the interface in a desired orientation, even to a large extent [17,[20][21][22].

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Section: Methodsmentioning

confidence: 99%

Asymmetry in melting and growth relaxation of⁴He crystals in superfluid after manipulation by acoustic radiation pressure

Nomura

Abe²,

Okuda

2017

New J. Phys.

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“…It is a heterogeneous nucleation, which is closely related to the depinning of a 4 He crystal pinned at that site on the wall [4][5][6][7][8][9][10][11]. Crystallization of 4 He in porous materials is elevated to a much higher pressure than that in the bulk [16][17][18][19][20][21][22].…”

mentioning

confidence: 99%

“…In classical materials, nucleation of a stable phase occurs via the thermal activation at high temperatures. In condensed phases of He, the thermal activation ceases and a quantum tunneling plays a role in the nucleation at a low enough temperature [2][3][4][5][6][7][8][9][10][11][12][13][14][15].…”

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confidence: 99%

Thermal and quantum nucleation of4He crystals in aerogel

et al. 2013

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“…6) As the seed crystal grew, it sometimes fell on the lower transducer with its facet parallel to the transducer surface. By this procedure, we were able to obtain the oriented crystal within several trials.…”

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Facet Growth of ⁴He Crystal Induced by Acoustic Waves

et al. 2006

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Very fast growth of the c-facet of a 4 He crystal was induced by acoustic waves. The growth velocity was larger at lower temperatures and saturated below about 400 mK. The velocity was proportional to the acoustic wave power. This fast growth cannot be explained by the spiral growth mechanism for the known value of the step mobility. We developed a step multiplication model for high-power acoustic waves and found reasonable agreement with the observed temperature and power dependence of the growth velocity.KEYWORDS: quantum solids, superfluid, acoustic radiation pressure, crystal growth, step DOI: 10.1143/JPSJ.75.023601A fundamental problem in crystal growth physics is how fast a facet can grow. In ordinary materials, the facet grows with a spiral growth mechanism well below the roughening transition temperature. 1) Step motion is limited by the diffusion of atoms and/or by the transport of latent heat. When two steps with opposite sign collide, they disappear without any reflection or transmission.Step density cannot increase indefinitely but reaches a steady-state value which is determined by the driving force for the crystallization. Recently, Parshin and Tsymbalenko have proposed a new type of collision of steps in the case of high mobility of steps at a large driving force.2) When high speed-steps collide, the steps pass through each other making another atomic layer on the facet due to the inertia of the liquid accompanying the step motion. This kinematical multiplication of steps makes the step density higher and the growth of the facet faster. Mobility of steps for a 4 He crystal in the superfluid liquid is not limited by the diffusion and can be very high at very low temperatures.3) We observed anomalously fast growth of the c-facet of a 4 He crystal induced by acoustic waves. The fast growth could not be explained by the spiral growth mechanisms and we possibly observed the multiplication of steps.We reported that acoustic waves induce crystallization of 4 He crystals at low temperatures. 4,5) We interpreted that this interface motion was induced by the acoustic radiation pressure. For the small displacement of the interface by a short acoustic wave pulse (1 ms), the acoustic radiation pressure model can explain the growth velocity of the rough and vicinal surfaces reasonably well at low temperatures by taking into account the orientation dependence of the growth coefficients. In this paper, we report the effect of the longer pulse (50 ms) applied to the vicinal surface from the crystal side. The displacement of the interface was much larger and the clear c-facet soon appeared on the top of the upheaval because the growth velocity of the c-facet was smaller than the vicinal surface. This growth velocity of the c-facet was much larger than the value expected from the spiral growth model with known step mobility. Since the pressure oscillation of the applied acoustic wave was large enough to accelerate steps to the velocity of sound, kinematical step multiplication was likely to occur. We constructed a g...

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Nucleation of crystals and superfluid droplets inHe4induced by acoustic waves

Cited by 15 publications

References 20 publications

Asymmetry in melting and growth relaxation of⁴He crystals in superfluid after manipulation by acoustic radiation pressure

Asymmetry in melting and growth relaxation of⁴He crystals in superfluid after manipulation by acoustic radiation pressure

Thermal and quantum nucleation of4He crystals in aerogel

Facet Growth of ⁴He Crystal Induced by Acoustic Waves

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Nucleation of crystals and superfluid droplets inHe4induced by acoustic waves

Cited by 15 publications

References 20 publications

Asymmetry in melting and growth relaxation of4He crystals in superfluid after manipulation by acoustic radiation pressure

Asymmetry in melting and growth relaxation of4He crystals in superfluid after manipulation by acoustic radiation pressure

Thermal and quantum nucleation of4He crystals in aerogel

Facet Growth of 4He Crystal Induced by Acoustic Waves

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Asymmetry in melting and growth relaxation of⁴He crystals in superfluid after manipulation by acoustic radiation pressure

Asymmetry in melting and growth relaxation of⁴He crystals in superfluid after manipulation by acoustic radiation pressure

Facet Growth of ⁴He Crystal Induced by Acoustic Waves