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Cheng ZG, Beamish J. Mass Flow through Solid ^{3}He in the bcc Phase. PHYSICAL REVIEW LETTERS 2018; 121:225304. [PMID: 30547618 DOI: 10.1103/physrevlett.121.225304] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 10/23/2018] [Indexed: 06/09/2023]
Abstract
A number of experiments have shown that mass can be transported through solid ^{4}He at temperatures as low as 16 mK, with features that suggest superflow. But the nature of this flow remains unclear. The Fermi isotope ^{3}He provides the possibility of a direct comparison to a solid in which quantum effects are even more important but superfluidity is not expected. We have made flow measurements on high purity bcc ^{3}He, using the same cell in which we observed a superfluidlike response in hcp ^{4}He when pressure differences were applied. We observed flow but, in marked contrast to ^{4}He, it decreased monotonically with temperature. Near melting, the flow was thermally activated with an energy of 0.85 K, but some flow remained even at 30 mK. The flow rates in the solid were essentially constant below 100 mK, even in low density samples that remelted at low temperatures. The very different behaviors of solid ^{3}He and ^{4}He support the interpretation of superflow in ^{4}He. Although such superflow is not possible in ^{3}He, the temperature-independent flow below 100 mK indicates that the flow in this regime also has a quantum origin. The flow must involve defects and, based on the magnitude of the flow and comparisons to other experiments, we conclude that in both the thermal and the quantum regimes the flow involves motion of dislocations via thermally activated or tunneling motion of kinks.
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Affiliation(s)
- Zhi Gang Cheng
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - John Beamish
- Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada
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Search for supersolidity in solid 4He using multiple-mode torsional oscillators. Proc Natl Acad Sci U S A 2016; 113:E3203-12. [PMID: 27222579 DOI: 10.1073/pnas.1605738113] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In 2004, Kim and Chan (KC) reported a decrease in the period of torsional oscillators (TO) containing samples of solid (4)He, as the temperature was lowered below 0.2 K [Kim E, Chan MHW (2004) Science 305(5692):1941-1944]. These unexpected results constituted the first experimental evidence that the long-predicted supersolid state of solid (4)He may exist in nature. The KC results were quickly confirmed in a number of other laboratories and created great excitement in the low-temperature condensed-matter community. Since that time, however, it has become clear that the period shifts seen in the early experiments can in large part be explained by an increase in the shear modulus of the (4)He solid identified by Day and Beamish [Day J, Beamish J (2007) Nature 450(7171):853-856]. Using multiple-frequency torsional oscillators, we can separate frequency-dependent period shifts arising from changes in the elastic properties of the solid (4)He from possible supersolid signals, which are expected to be independent of frequency. We find in our measurements that as the temperature is lowered below 0.2 K, a clear frequency-dependent contribution to the period shift arising from changes in the (4)He elastic properties is always present. For all of the cells reported in this paper, however, there is always an additional small frequency-independent contribution to the total period shift, such as would be expected in the case of a transition to a supersolid state.
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Fear MJ, Walmsley PM, Chorlton DA, Zmeev DE, Gillott SJ, Sellers MC, Richardson PP, Agrawal H, Batey G, Golov AI. A compact rotating dilution refrigerator. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2013; 84:103905. [PMID: 24182127 DOI: 10.1063/1.4822340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We describe the design and performance of a new rotating dilution refrigerator that will primarily be used for investigating the dynamics of quantized vortices in superfluid (4)He. All equipment required to operate the refrigerator and perform experimental measurements is mounted on two synchronously driven, but mechanically decoupled, rotating carousels. The design allows for relative simplicity of operation and maintenance and occupies a minimal amount of space in the laboratory. Only two connections between the laboratory and rotating frames are required for the transmission of electrical power and helium gas recovery. Measurements on the stability of rotation show that rotation is smooth to around 10(-3) rad s(-1) up to angular velocities in excess of 2.5 rad s(-1). The behavior of a high-Q mechanical resonator during rapid changes in rotation has also been investigated.
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Affiliation(s)
- M J Fear
- School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
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Sinha D, Sengupta S, Dasgupta C, Valls OT. Out of equilibrium plasticity dynamics and the annealing of supersolidity in solid ⁴He. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:295601. [PMID: 23803347 DOI: 10.1088/0953-8984/25/29/295601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We present a numerical study of a continuum plasticity field coupled to a Ginzburg-Landau model for superfluidity. The results suggest that a supersolid fraction may appear as a long-lived transient during the time evolution of the plasticity field at higher temperatures where both dislocation climb and glide are allowed. Supersolidity, however, vanishes with annealing. As the temperature is decreased, dislocation climb is arrested and any residual supersolidity due to incomplete annealing remains frozen. Our results may provide a resolution of many perplexing issues concerning a variety of experiments on bulk solid (4)He.
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Affiliation(s)
- Debabrata Sinha
- TIFR Centre for Interdisciplinary Sciences, 21 Brundavan Colony, Narsingi, Hyderabad 500075, India
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Shin H, Kwon Y. Effects of 3He impurities on the superfluid response of the 4He monolayer on a C20 molecule. J Chem Phys 2013; 138:064307. [PMID: 23425471 DOI: 10.1063/1.4792204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The path-integral Monte Carlo calculations have been performed to investigate the effects of (3)He impurities on structural and superfluid properties of the (4)He monolayer on a single C(20) molecule. According to our previous study, the helium monolayer exhibits different quantum states for different numbers of (4)He adatoms and is completed to form a commensurate solid where nanoscale supersolidity can be realized through the activation of mobile vacancy states. We first observe that different structures for different numbers of helium atoms are mostly preserved with the replacement of a few (4)He atoms with the same number of (3)He atoms, whether the helium layer is a fluid or a solid. However, the substitution of (3)He impurities is found to have different effects on the superfluid response of the helium layer, depending on its quantum state. For a partially-filled fluid layer the superfluid fraction decreases monotonically with the increasing (3)He concentration, which can be understood in terms of the suppression of exchange couplings among (4)He atoms due to the presence of (3)He impurities. On the other hand, the substitution of a few (3)He impurity atoms may increase the superfluid fraction of a near-complete monolayer that is in a crystalline solid state. The enhancement of superfluidity in a solid layer is interpreted to be due to interstitial and vacancy defects promoted by larger quantum fluctuations of lighter (3)He atoms. This provides strong evidence that the (4)He monolayer on C(20) shows the vacancy-based supersolidity near its completion.
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Affiliation(s)
- Hyeondeok Shin
- Division of Quantum Phases and Devices, School of Physics, Konkuk University, Seoul 143-701, South Korea
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Proponent of supersolid helium joins sceptics. Nature 2012. [DOI: 10.1038/nature.2012.11609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Kim DY, Chan MHW. Absence of supersolidity in solid helium in porous Vycor glass. PHYSICAL REVIEW LETTERS 2012; 109:155301. [PMID: 23102323 DOI: 10.1103/physrevlett.109.155301] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Indexed: 06/01/2023]
Abstract
In 2004, Kim and Chan carried out torsional oscillator measurements of solid helium confined in porous Vycor glass and found an abrupt drop in the resonant period below 200 mK. The period drop was interpreted as probable experimental evidence of nonclassical rotational inertia. This experiment sparked considerable activities in the studies of superfluidity in solid helium. More recent ultrasound and torsional oscillator studies, however, found evidence that shear modulus stiffening is responsible for at least a fraction of the period drop found in bulk solid helium samples. The experimental configuration of Kim and Chan makes it unavoidable to have a small amount of bulk solid inside the torsion cell containing the Vycor disk. We report here the results of a new helium in Vycor experiment with a design that is completely free from any bulk solid shear modulus stiffening effect. We found no measurable period drop that can be attributed to nonclassical rotational inertia.
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Affiliation(s)
- Duk Y Kim
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Mason P, Josserand C, Rica S. Activated nucleation of vortices in a dipole-blockaded supersolid condensate. PHYSICAL REVIEW LETTERS 2012; 109:045301. [PMID: 23006094 DOI: 10.1103/physrevlett.109.045301] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Indexed: 06/01/2023]
Abstract
We investigate theoretically and numerically a model of a supersolid in a dipole-blockaded Bose-Einstein condensate. The dependence of the superfluid fraction with an imposed thermal bath and a uniform boost velocity on the condensate is considered. Specifically, we observe a critical velocity for the nucleation of vortices in our system that is strongly linked to a steplike decrease in the superfluid fraction. We are able to use a scaling argument based on the energy required to activate a vortex, relating the critical temperature to the critical velocity, and find that this relationship is in good agreement with the numerical simulations carried out on the nonlocal Gross-Pitaevskii equation.
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Affiliation(s)
- Peter Mason
- Department of Physics, Durham University, Durham DH1 3LE, United Kingdom
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Henkel N, Cinti F, Jain P, Pupillo G, Pohl T. Supersolid vortex crystals in Rydberg-dressed Bose-Einstein condensates. PHYSICAL REVIEW LETTERS 2012; 108:265301. [PMID: 23004994 DOI: 10.1103/physrevlett.108.265301] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Indexed: 06/01/2023]
Abstract
We study rotating quasi-two-dimensional Bose-Einstein condensates, in which atoms are dressed to a highly excited Rydberg state. This leads to weak effective interactions that induce a transition to a mesoscopic supersolid state. Considering slow rotation, we determine its superfluidity using quantum Monte Carlo simulations as well as mean field calculations. For rapid rotation, the latter reveal an interesting competition between the supersolid crystal structure and the rotation-induced vortex lattice that gives rise to new phases, including arrays of mesoscopic vortex crystals.
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Affiliation(s)
- N Henkel
- Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany
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Choi H, Takahashi D, Choi W, Kono K, Kim E. Staircaselike suppression of supersolidity under rotation. PHYSICAL REVIEW LETTERS 2012; 108:105302. [PMID: 22463420 DOI: 10.1103/physrevlett.108.105302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Indexed: 05/31/2023]
Abstract
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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Affiliation(s)
- H Choi
- Department of Physics and Center for Supersolid and Quantum Matter Research, KAIST, Daejeon 305-701, Republic of Korea
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