Observation of hidden phases in supersolid 4He

Choi, Hyoungsoon; Kwon, Soon-Yong; Dy, Kim; Kim, Eunseong

doi:10.1038/nphys1630

Cited by 21 publications

(28 citation statements)

References 22 publications

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“…However, the NCRI did not increase until a substantially larger TO amplitude was applied at low temperature. A similar hysteresis was also reported in a number of TO experiments [13][14][15][16]. The hysteresis between the drive-up sweep and the drive-down sweep disappeared at temperatures above about 60 mK.…”

supporting

confidence: 84%

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Stress- and temperature-dependent hysteresis of the shear modulus of solid helium

Kang

Kim

et al. 2013

Phys. Rev. B

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The shear modulus of solid 4 He below 200 mK exhibits an unusual increase, the characteristics of which show remarkable similarities to those of the period reduction in torsional oscillator experiments. We systematically studied the drive strain and temperature dependence of the shear modulus at low temperatures. The hysteretic behavior depends strongly on the drive and cooling history, which can be associated with the thermally assisted Granato-Lucke dislocation theory. The phase diagram of the shear modulus is constructed on the basis of the emerging hysteretic behavior.An anomalous increase in the shear modulus at low temperatures was recently observed in solid helium [1]. The anomaly exhibits temperature, frequency, and 3 He concentration dependences resembling those of the nonclassical rotational inertia (NCRI) in torsional oscillator (TO) experiments [2,3]. These remarkable similarities have attracted theoretical and experimental attention [4,5]. For instance, a dislocation vibration model for the NCRI is proposed. The temperature dependence of the period of a torsional oscillator containing solid helium is derived from the variation in the average pinning length of dislocations in solid helium [6]. Other efforts to provide a non-supersolid explanation for the TO response were also motivated by the similarities between the two phenomena [4,5,7,8]. The Cornell group recently reported that the TO motion was controlled by the same microscopic excitation that is agitated by temperature and stress independently, which they suggested can be understood within the framework of a dissipation model in which the elastic properties change at low temperatures [9]. Nevertheless, the resonant period reduction found in some earlier TO measurements, including Ref.[9], can be ascribed to the change in the elastic properties of solid helium filling a torsion rod [10]. Thus, the similar response of TO to the drive and temperature agitation can be understood in terms of the dislocation pinning mechanism.The shear modulus increase can be interpreted as the pinning of dislocations by 3 He impurities according to the Granato-Lucke (GL) dislocation theory [11]. The original GL theory considers only the unpinning of dislocations by applied stress without a thermal-fluctuationinduced unbinding mechanism: a large stress reduces the number of pinning points by detaching 3 He impurities from dislocations, thus suppressing the shear modulus. Nevertheless, the effects of stress and temperature on the shear modulus are similar, so its temperature dependence can be explained by the variation in the dislocation loop length with progressive lengthening of freely vibrating dislocation segments due to thermal evaporation of 3 He impurities [1,6,12]. Moreover, the softening of the shear modulus is not a phase transition but a crossover of the thermally activated relaxation process from a stiff (pinned) state to a relaxed (unpinned) state.The discrepancy in the effects of the drive stress and temperature appears when the hysteretic behaviors dur...

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supporting

confidence: 84%

“…The shape of the shear modulus phase diagram is similar to that of NCRI [16]. It is probably reasonable to say that the phenomena are connected, considering their similarities in many properties, including the phase diagram resemblance.…”

mentioning

confidence: 62%

Stress- and temperature-dependent hysteresis of the shear modulus of solid helium

Kang

Kim

et al. 2013

Phys. Rev. B

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“…The initial discoveries of the NCRI were later confirmed and expanded upon by many others [5,6,7,8,9,10]. In addition, an increase of the shear modulus [11] and recently mass flow in the solid [12] in the same temperature range were reported.…”

mentioning

confidence: 70%

“…The loaded Q of this TO is about 5 × 10 5 . In the earlier versions, the annular He cell was made of 7075 Al alloy, with a Q close to 10 6 . The annular He space has an outer diameter of 17mm, a width of 2mm , and a total volume of 1cc.…”

Section: Experimental Systemmentioning

confidence: 99%

On the Mobile Behavior of Solid 4He at High Temperatures

Eyal¹,

Polturak²

2011

J Low Temp Phys

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We report studies of solid helium contained inside a torsional oscillator, at temperatures between 1.07K and 1.87K. We grew single crystals inside the oscillator using commercially pure 4 He and 3 He-4 He mixtures containing 100 ppm 3 He. Crystals were grown at constant temperature and pressure on the melting curve. At the end of the growth, the crystals were disordered, following which they partially decoupled from the oscillator. The fraction of the decoupled He mass was temperature and velocity dependent. Around 1K, the decoupled mass fraction for crystals grown from the mixture reached a limiting value of around 35%. In the case of crystals grown using commercially pure 4 He at temperatures below 1.3K, this fraction was much smaller. This difference could possibly be associated with the roughening transition at the solid-liquid interface.

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“…Another interesting observation of solid 4 He is that the resonant period of a torsional oscillator (TO) containing solid 4 He decreases below 0.2 K [13][14][15][16][17][18][19][20][21][22][23][24][25]. This was initially interpreted as a result of the reduction of the rotational inertia of solid 4 He, and considered as the appearance of a putative supersolid phase.…”

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confidence: 99%

Simultaneous investigation of shear modulus and torsional resonance of solidHe4

Shin¹,

Choi²,

Shirahama

et al. 2016

Phys. Rev. B

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We investigate the origin of a resonant period drop of a torsional oscillator (TO) containing solid 4 He by inspecting its relation to a change in elastic modulus. To understand this relationship directly, we measure both phenomena simultaneously using a TO with a pair of concentric piezoelectric transducers inserted in its annulus. Although the temperature, 3 He concentration, and frequency dependence are essentially the same, a marked discrepancy in the drive amplitude dependence is observed. We find that this discrepancy originates from the anisotropic response of polycrystalline solid 4 He connected with low-angle grain boundaries by studying the shear modulus parallel to and perpendicular to the driving direction.The change in the shear modulus µ and the dissipation Q −1 of solid 4 He at low temperature [1-9] have been understood thoroughly by the Granato-Lucke (GL) model [10][11][12]. According to this model, in a dislocation network, dislocations glides under applied stress, which leads to an additional strain field. This strain decreases the µ of a solid from its intrinsic value. However, the slip motion can be effectively damped by binding of dislocation segments with impurities at low temperatures. The pinning of dislocations is regulated by the finite binding energy, E b , between dislocations and impurities in a solid, such that the pinning can be promoted only at sufficiently low temperatures. These weakly bound impurities on the dislocations are detached as a result of increasing temperature and/or external stress, which can be described by the Debye relaxation process and characterized by a relaxation time τ and an activation energy E b [4,8,9]. Solid 4 He is a golden testbed for the GL model because the only impurities in solid 4 He are an extremely low concentration of 3 He atoms. The properties of dislocation in solid 4 He, such as the average network length, dislocation density, and length distribution have been extensively studied by .Another interesting observation of solid 4 He is that the resonant period of a torsional oscillator (TO) containing solid 4 He decreases below 0.2 K [13][14][15][16][17][18][19][20][21][22][23][24][25]. This was initially interpreted as a result of the reduction of the rotational inertia of solid 4 He, and considered as the appearance of a putative supersolid phase. Nevertheless, both the µ and TO response exhibited fundamentally identical dependences on the temperature, driving amplitude, frequency, and amount of 3 He impurities [1,25,26]. To investigate the underlying relationships between them, Kim et al.[25] measured the shear modulus change (∆µ) and the resonant period drop (∆prd) simultaneously by inserting a pair of flat piezoelectric transducers (PZT) into the center of a TO. Even though a similar temperature dependence was observed, the drive amplitude responses were different. When a large AC voltage was applied to a driving transducer, the ∆µ of solid 4 He at the center channel was fully suppressed, but the shift in the resonance period of the TO was ...

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Observation of hidden phases in supersolid 4He

Cited by 21 publications

References 22 publications

Stress- and temperature-dependent hysteresis of the shear modulus of solid helium

Stress- and temperature-dependent hysteresis of the shear modulus of solid helium

On the Mobile Behavior of Solid 4He at High Temperatures

Simultaneous investigation of shear modulus and torsional resonance of solidHe4

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