A neutron scattering study of hydrogen in vycor glass

X-ray diffraction experiments show that solid 4He grown in aerogel is highly polycrystalline, with an hcp crystal structure (as in bulk) and a crystallite size of approximately 100 nm. In contrast to the expectation that the highly disordered solid will have a large supersolid fraction, torsional oscillator measurements show a behavior that is strikingly similar to high purity crystals grown from the superfluid phase. The low temperature supersolid fraction is only approximately 3 x 10(-4), and the onset temperature is approximately 100 mK.

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“…A typical diffraction peak measured with high resolution is shown in Fig. 2 Similar behavior has been seen in other porous media [26,27].…”

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confidence: 76%

Torsional Oscillator and Synchrotron X-Ray Experiments on SolidHe4in Aerogel

et al. 2008

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“…4). In contrast, no such a peak develops if crystallization occurs inside the cavities, as observed experimentally [9].…”

Section: Discussionmentioning

confidence: 54%

“…However, attempts to supercool liquid hydrogen by embedding it in a vycor matrix failed to yield any evidence of superfluid behavior [7,8]. Indeed, neutron scattering studies of p-H 2 in vycor glass at low temperature suggest that the system crystallizes in the pores, albeit with a different crystal structure [9], a fact that can be attributed to the irregular geometry as well as to the strong attraction exerted on the p-H 2 molecules by the pore surface, where the crystal phase nucleates. It should also be mentioned that experimentally one observes the lowering of the superfluid transition temperature of liquid helium confined in vycor [10], to indicate that, while stabilizing the liquid phase, confinement has also the effect of suppressing superfluidity.…”

Section: Introductionmentioning

confidence: 99%

Enhanced superfluid response of parahydrogen in nanoscale confinement

Omiyinka¹

2014

Phys. Rev. B

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Confinement has generally the effect of suppressing order in condensed matter. Indeed, phase transitions such as freezing, or the superfluid transition in liquid helium, occur at lower temperatures in confinement than they do in the bulk. We provide here an illustration of a physical setting in which the opposite takes place. Specifically, the enhancement of the superfluid response of parahydrogen confined to nanoscale size cavities is demonstrated by means of first principle computer simulations. Prospects to stabilize and observe the long sought but yet elusive bulk superfluid phase of parahydrogen in purposefully designed porous media are discussed.Comment: 5 pages, 4 figures in colo

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“…One of the a priori more interesting options was to confine hydrogen in a porous media, like a vykor glass, with pores in the nanometer scale. However, the lowest temperature at which the system was detected to be liquid was T ∼ 8 K and so still far from the pursued superfluid [5].…”

Section: Introductionmentioning

confidence: 99%

Luttinger parameter of quasi-one-dimensional para−H2

2017

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We have studied the ground-state properties of para-hydrogen in one dimension and in quasione-dimensional configurations using the path integral ground state Monte Carlo method. This method produces zero-temperature exact results for a given interaction and geometry. The quasione-dimensional setup has been implemented in two forms: the inner channel inside a carbon nanotube coated with H2 and a harmonic confinement of variable strength. Our main result is the dependence of the Luttinger parameter on the density within the stable regime. Going from one dimension to quasi-one dimension, keeping the linear density constant, produces a systematic increase of the Luttinger parameter. This increase is however not enough to reach the superfluid regime and the system always remain in the quasi-crystal regime, according to Luttinger liquid theory.

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A neutron scattering study of hydrogen in vycor glass

Cited by 38 publications

References 19 publications

Torsional Oscillator and Synchrotron X-Ray Experiments on SolidHe4in Aerogel

Torsional Oscillator and Synchrotron X-Ray Experiments on SolidHe4in Aerogel

Enhanced superfluid response of parahydrogen in nanoscale confinement

Luttinger parameter of quasi-one-dimensional para−H2

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