Observation of a glassy phase of<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>in the region of supersolid effects

Grigor’ev, V. N.; Maı̆danov, V. A.; Rubanskii, V. Yu.; Rubets, S. P.; Rudavskiı̆, É. Ya.; Rybalko, A. S.; Syrnikov, Ye. V.; Tikhii, V. A.

doi:10.1103/physrevb.76.224524

Cited by 50 publications

(48 citation statements)

References 38 publications

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“…By truncating the TLS DOS above a characteristic cutoff energy E c , the bump-like feature in δC can fairly well be captured within the scatter and uncertainty of the data. Furthermore, our thermodynamic analysis results in Debye temperatures Θ D and TLS DOS D 0 that are in qualitative agreement with known P (T ) measurements in the solid [34,35]. This suggests the possibility of a glassy subsystem at the ppm level in hcp 4 He crystals.…”

Section: Discussionsupporting

confidence: 88%

“…This suggests the possibility of a glassy subsystem at the ppm level in hcp 4 He crystals. The presence of a glassy subsystem is consistent with recent reports of long relaxation times in torsion oscillators [12], P vs. T measurements [34,35], and transport measurements [16,17]. In order to uniquely determine the ground state of solid 4 He, i.e., whether it exhibits a supersolid or glass transition, more accurate measurements of the specific heat and thermal conductivity at lower temperatures and up to 0.5 K are needed.…”

Section: Discussionsupporting

confidence: 81%

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A Glassy Contribution to the Heat Capacity of hcp 4He Solids

Graf

Balatsky

2010

J Low Temp Phys

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We model the low-temperature specific heat of solid 4 He in the hexagonal closed packed structure by invoking two-level tunneling states in addition to the usual phonon contribution of a Debye crystal for temperatures far below the Debye temperature, T < Θ D /50. By introducing a cutoff energy in the two-level tunneling density of states, we can describe the excess specific heat observed in solid hcp 4 He, as well as the low-temperature linear term in the specific heat. Agreement is found with recent measurements of the temperature behavior of both specific heat and pressure. These results suggest the presence of a very small fraction, at the parts-per-million (ppm) level, of two-level tunneling systems in solid 4 He, irrespective of the existence of supersolidity.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionsupporting

confidence: 81%

A Glassy Contribution to the Heat Capacity of hcp 4He Solids

Graf

Balatsky

2010

J Low Temp Phys

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“…A further increase in the temperature to 2.0 K produces a further drop in pressure with a much faster relaxation time. The reduction in pressure during the annealing of disordered solid 4 He samples is not a new phenomenon, but has been reported a number of times by other experimenters, most recently by [16] in a paper reporting evidence for a glassy phase in 4 He samples grown by the blocked capillary method.…”

Section: Fig 1: Torsional Oscillatormentioning

confidence: 89%

Disorder and the Supersolid State of SolidHe4

2007

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We report torsional oscillator supersolid studies of highly disordered samples of solid 4 He. In an attempt to approach the amorphous or glassy state of the solid, we prepare our samples by rapid freezing from the normal phase of liquid 4 He. Less than two minutes is required for the entire process of freezing and the subsequent cooling of the sample to below 1 K. The supersolid signals observed for such samples are remarkably large, exceeding 20 % of the entire solid helium moment of inertia. These results, taken with the finding that the magnitude of the small supersolid signals observed in our earlier experiments can be reduced to an unobservable level by annealing, strongly suggest that the supersolid state exists for the disordered or glassy state of helium and is absent in high quality crystals of solid 4 He. Following the discovery by Kim and Chan (KC) [1, 2] of the supersolid or nonclassical rotational inertia (NCRI) state of bulk solid 4 He, several independent groups using the same torsional oscillator technique have confirmed the KC supersolid results. These include the Japanese groups of Shirahama et al. [3], working at Keio University, and Kubota et al. [4] at the ISSP, as well as our group [5] at Cornell University. In these early experiments, the solid samples were formed by the blocked capillary technique. In this method the fill line to the cell is first allowed to freeze ensuring that solidification in the cell occurs under a condition of constant average density. This technique is known to produce relatively disordered polycrystalline samples. The signals observed in the early experiments were small representing, at most, a few percent of the total solid helium mass. The Cornell experiments [5] also demonstrated that the supersolid signal could be substantially reduced through annealing of the sample. In some cases the annealing process appeared to eliminate the supersolid signal; i.e., it reduced the supersolid fraction below the 0.05% level of experimental detection. This signal reduction upon annealing strongly suggested that sample disorder plays an important role in supersolid phenomena. This inference is supported by more recent work by Chan's group [6] where high quality crystals were grown under conditions of constant pressure. The supersolid signals observed for these constant pressure samples were somewhat smaller in magnitude than those obtained for more disordered samples created in the same cell by the blocked capillary method.Recently, there has been a growing consensus in the theoretical community [7,8,9,10] that an ideal hcp helium crystal will not exhibit the supersolid phenomenon, but rather, some form of disorder such as vacancies, interstitials, superfluid grain boundaries [11,12], or perhaps a glassy or superglass phase [13,14] is required for the existence of the supersolid state. A summary of the current theoretical literature is given in a recent review [15]. FIG. 1: Torsional oscillator:The motion of the torsion bob is excited and detected electrostatically. A Straty...

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“…The fact that crystals grown at a constant temperature or pressure 69) exhibited NCRI means that grain boundaries are not essential for NCRI, and other defects must be important. This also excludes the possibility that the metastable glassy region of 4 He, which may be present in a rapidly quenched sample, 76) can play the decisive role in these phenomena. Dislocations are reasonable candidates, since it is known that even in a single crystal the density of dislocations can vary by a large amount depending on experimental conditions.…”

Section: Special Topicsmentioning

confidence: 91%

Solid ⁴He and the Supersolid Phase: from Theoretical Speculation to the Discovery of a New State of Matter? –A Review of the Past and Present Status of Research–

Galli

Reatto

2008

J. Phys. Soc. Jpn.

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The possibility of a supersolid state of matter, i.e., a crystalline solid exhibiting superfluid properties, first appeared in theoretical studies about forty years ago. After a long period of little interest due to the lack of experimental evidence, it has attracted strong experimental and theoretical attention in the last few years since Kim and Chan (Penn State, U.S.A.) reported evidence for nonclassical rotational inertia effects, a typical signature of superfluidity, in samples of solid 4 He. Since this ''first observation'', other experimental groups have observed such effects in the response to the rotation of samples of crystalline helium, and it has become clear that the response of the solid is extremely sensitive to growth conditions, annealing processes, and 3 He impurities. A peak in the specific heat in the same range of temperatures has been reported as well as anomalies in the elastic behaviour of solid 4 He with a strong resemblance to the phenomena revealed by torsional oscillator experiments. Very recently, the observation of unusual mass transport in hcp solid 4 He has also been reported, suggesting superflow. From the theoretical point of view, powerful simulation methods have been used to study solid 4 He, but the interpretation of the data is still rather difficult; dealing with the question of supersolidity means that one has to face not only the problem of the coexistence of quantum coherence phenomena and crystalline order, exploring the realm of spontaneous symmetry breaking and quantum field theory, but also the problem of the role of disorder, i.e., how defects, such as vacancies, impurities, dislocations, and grain boundaries, participate in the phase transition mechanism.

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Observation of a glassy phase ofHe4in the region of supersolid effects

Cited by 50 publications

References 38 publications

A Glassy Contribution to the Heat Capacity of hcp 4He Solids

A Glassy Contribution to the Heat Capacity of hcp 4He Solids

Disorder and the Supersolid State of SolidHe4

Solid ⁴He and the Supersolid Phase: from Theoretical Speculation to the Discovery of a New State of Matter? –A Review of the Past and Present Status of Research–

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Observation of a glassy phase ofHe4in the region of supersolid effects

Cited by 50 publications

References 38 publications

A Glassy Contribution to the Heat Capacity of hcp 4He Solids

A Glassy Contribution to the Heat Capacity of hcp 4He Solids

Disorder and the Supersolid State of SolidHe4

Solid 4He and the Supersolid Phase: from Theoretical Speculation to the Discovery of a New State of Matter? –A Review of the Past and Present Status of Research–

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Solid ⁴He and the Supersolid Phase: from Theoretical Speculation to the Discovery of a New State of Matter? –A Review of the Past and Present Status of Research–