Liquefaction of second-layer<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">He</mml:mi></mml:mrow><mml:mprescripts /><mml:mrow /><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow /><mml:mrow /></mml:mmultiscripts></mml:mrow></mml:math>films on graphite

Polanco, S. E.; Bretz, Michael

doi:10.1103/physrevb.17.151

Cited by 44 publications

(43 citation statements)

References 16 publications

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“…(1) for ρ This value is in agreement with previous simulation results of Whitlock, 25 who used an effective potential for second layer particles. It is also compatible with neutron diffraction experiments and heat capacity measurements, 10,11,13,19 where values in the range 0.112-0.115Å −2 were found.…”

supporting

confidence: 87%

“…The second layer is known to exhibit a gas, a superfluid and an incommensurate solid phase, as shown by heat capacity measurements 15,19 and neutron diffraction experiments. 10,11,12 At intermediate density between these two phases, Greywall and Busch conjectured a commensurate solid with a √ 7 × √ 7 partial registry with respect to the first layer, based on their heat capacity measurements.…”

mentioning

confidence: 99%

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Phase diagram ofH4eadsorbed on graphite

et al. 2008

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We present results of a theoretical study of 4 He films adsorbed on graphite, based on the continuous space worm algorithm. In the first layer, we find a domain-wall phase and a (7/16) registered structure between the commensurate (1/3) and the incommensurate solid phases. For the second layer, we find only superfluid and incommensurate solid phases. The commensurate phase found in previous simulation work is only observed if first layer particles are kept fixed; it disappears upon explicitly including their zero-point fluctuations. No evidence of any "supersolid" phase is found.

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confidence: 87%

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confidence: 99%

Phase diagram ofH4eadsorbed on graphite

et al. 2008

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“…The data show again a kink structure at ρ 1→2 at lower temperatures. The overall behavior is similar to that with Grafoil by previous workers 9 . The chemical potential µ 2 of the 2nd layer (ρ >12 nm −2 ) is nearly density independent at ≈ −30 K. In addition, this value is in good agreement with existing theoretical calculations by Corboz et al 10 denoted by a horizontal dotted line and by Whitlock et al 11 denoted by a horizontal dashed line in the figure. On the other hand, the chemical potential µ 1 of the 1st layer (ρ <12 nm −2 ) seems to be consistently lower than the same theoretical calculations.…”

Section: The 2nd-layer Promotionsupporting

confidence: 74%

Preliminary Heat Capacity and Vapor Pressure Measurements of 2D 4He on ZYX Graphite

Nakamura

Matsui

et al. 2013

J Low Temp Phys

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We report preliminary heat capacity and vapor pressure measurements of the first and second layers of 4 He adsorbed on ZYX graphite. ZYX is known to have much better crystallinity than Grafoil, the most commonly-used exfoliated graphite substrate, such as a ten-times larger platelet size. This allows us to distinguish different phases in 2D 4 He much more clearly and may provide qualitatively different insights into this system. We found a significantly asymmetric density-dependence of the heat-capacity peak associated with the √ 3 × √ 3 phase formation comparing with that obtained with Grafoil. The 2nd-layer promotion density is determined as 11.8 ± 0.3 nm −2 from the heat-capacity measurement of low density samples in the 2nd layer and vapor pressure measurement.

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“…It seems difficult to argue that the single feature observed is not the KT maximum but simply the discontinuity rounded by substrate heterogeneity and thermal excitations in the liquid state [8]. This is not only because of the fine agreement with the theoretical calculations, but also because the peak amplitude should then be quite sensitive to the particular graphite substrate used, and yet all experiments give essentially the same results.…”

Section: Dennis S Greywall and Paul A Busch A Tand T Bell Laboratoriementioning

confidence: 81%

“…At present, the consensus appears to be that this "peak" corresponds to the crossing of a phase boundary separating 2D vapor at high temperature and a vapor condensed-phase coexistence region at lower temperature. Although this condensed phase was once thought to be the 2D liquid state [7,8], it is now usually taken to be the R phase; see Fig. 1 (a) [9].…”

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confidence: 99%

Heat capacity of fluid monolayers ofHe4

1991

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The heat capacity of "^He adsorbed on graphite has been precisely measured over a fine grid of coverages for temperatures extending down to 100 mK and for coverages up to five atomic layers. The data indicate that the two-dimensional liquid is self-bound in each of the first three layers with an areal density of about 0.04 atom/A^. There is also evidence suggesting that this liquid undergoes a KosterlitzThouless transition.PACS numbers: 67.70.+n, 67.40.Kh The submonolayer phase diagrams of ^He and "^He adsorbed on graphite appear remarkably similar [1] for areal densities greater than that corresponding to the VJ registered phase R, At lower coverages, however, the generally accepted "^He diagram [1-3] differs substantially from that recently proposed [4,5] for ^He. Here ^He heat-capacity data [4] indicate that this system exists as a two-dimensional (2D) fluid F, down to presumably absolute zero, although there is evidence suggesting some type of phase transition near 3 mK. In contrast, low-coverage heat-capacity data for "^He exhibit a rounded maximum near 1 K which has been ascribed to many different phenomena [6]. At present, the consensus appears to be that this "peak" corresponds to the crossing of a phase boundary separating 2D vapor at high temperature and a vapor condensed-phase coexistence region at lower temperature. Although this condensed phase was once thought to be the 2D liquid state [7,8], it is now usually taken to be the R phase; see Fig. 1 (a) [9]. The low-coverage "^He system at temperatures less than 1 K is thus expected to be in a two-phase region bounded by the pure 2D gas phase near zero coverage and by the pure R phase at PR (0.0637 atom/A^) even though there is no convincing evidence from either scattering or thermodynamic experiments to substantiate this belief. However, given the quantitative similarities between the ^He and "^He phase diagrams in the vicinity of the registered phase, the recent heatcapacity results for ^He raise several questions and doubts about the interpretation of the "^He phase diagram. The very-low-temperature ^He data show unambiguously that this system enters into a two-phase region only near PR and that the broad portion of the phase diagram associated with the registered phase is actually an F'R coexistence region. In the "^He picture the corresponding region of the phase diagram is thought to be the registered phase existing with as much as 30% vacancies [2].In this Letter we present new low-temperature heatcapacity data for "^He/graphite which contradict the current view and indicate a two-phase region involving the R phase which is restricted, as for submonolayer ^He, to 0.04;Sp;Sp/?; see Fig. 1(b). At lower coverages there is a coexistence of the 2D gas and the liquid which is believed to be superfluid. We also have evidence at much higher coverages suggesting that each of the next several atomic layers undergoes a similar evolution with increasing layer density. The new results are based on precise heat-capacity measurements which extend to lower tempe...

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Liquefaction of second-layerHe4films on graphite

Cited by 44 publications

References 16 publications

Phase diagram ofH4eadsorbed on graphite

Phase diagram ofH4eadsorbed on graphite

Preliminary Heat Capacity and Vapor Pressure Measurements of 2D 4He on ZYX Graphite

Heat capacity of fluid monolayers ofHe4

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