Phases of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">He</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">He</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>Monolayer Films Adsorbed on Basal-Plane Orien

Bretz, Michael; Dash, J. G.; Hickernell, D. C.; McLean, E. O.; Vilches, O. E.

doi:10.1103/physreva.8.1589

Cited by 436 publications

(99 citation statements)

References 78 publications

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“…Their prediction was that the bands are nearly free-particle~like, with only narrow gaps, corresponding to an input potential which varies relatively little across the surface. This was consistent with specific heat data at low coverage (Bretz et al, 1973), which approached the 2D hightemperature limit C =NkB for T"" 4 K (Dash and Schick, 1979). Very recently, however, the scattering data of and of Derry et al:-(1979) have implied that the potential is more corrugated than was previously believed, due to the anisotropic covalent bonding of graphite Cole, 1980a, 1980b).…”

supporting

confidence: 77%

“…For another, a sharp heat capacity peak observed at roughly 3 K and 0.6 layers (in both 3 He and 4 He) turned out to be due to a lattice-gas ordering transition to a phase having one helium atom occupying every third carbon hexagon in the plane (Bretz et al, 1973). Since the lattice constant of graphite is well known, the ordering peak at the critical coverage N • affords a means of making a precise evaluation of the surface area of any Grafoil sample.…”

Section: Ill Thermodynamic Measurements a Binding E~;~ergymentioning

confidence: 99%

“…When the special properties of Grafoil as a substrate were first found (Bretz and Dash, 1971), the quantitatively uncertain situation improved dramatically in a number of ways. For one thing it was found that measurements were highly reproducible in different laboratories (Bretz et al, i973;Elgin and Goodstein, 1974).…”

Section: Ill Thermodynamic Measurements a Binding E~;~ergymentioning

confidence: 99%

“…)tivation for interest in thi$ problem .derived from the discovery Duval, 1969, 1970;Bretz and Dash, 1971) that exfoliated graphite presents a uniquely homogeneous substrate for studies of physically absorbed monolayer films. In particular, films of =i!e and 4 He absorbed on a commerCial product called Grafoil 1 were found to exhibit a rich variety of phases, transitions, and other phenomena (Bretz e t al., 1973;Elgin and Goodstein, 1974;Dash and Schick, 1979).…”

Section: Introductionmentioning

confidence: 99%

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Probing the helium-graphite interaction

1981

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Two separate lines of investigation have recently converged to produce a highly detailed picture of the behavior of helium atoms physisorbed on graphite basal plane surfaces. Atomic beam scattering experiments on single crystals have yielded accurate values for the binding energies of several· states for both 4 He and 'He, as well as matrix elements of the largest Fourier component of the periodic part of the interaction potential. From these data, a complete three-dimensional description of the potential has been constructed, and the energy band structure of a helium atom moving in this potential calculated. At the same time, accurate thermodynamic measurements were made on submonolayer helium films adsorbed on Grafoil .. The binding energy and low-coverage specific heat deduced from these measurements are in excellent agreement with those calculated from the band structures.

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supporting

confidence: 77%

Section: Ill Thermodynamic Measurements a Binding E~;~ergymentioning

confidence: 99%

Section: Ill Thermodynamic Measurements a Binding E~;~ergymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Probing the helium-graphite interaction

1981

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“…Moreover, the second layer of 3 He should be the best representative of monolayer 3 He on graphite without heterogeneities. According to the previous experimental [24] and theoretical [9] determinations of the second layer promotion density of 4 He (11.4 ∼ 11.8 nm −2 ), we expect that a small fraction (0.3 ∼ 0.7 nm −2 ) of 4 He is promoted to the second layer and preferentially occupies deeper potential sites above the substrate heterogeneities. This explains why we don't observe C amor nor a sizable intervening region prior to the puddle region in the second-layer measurement.…”

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confidence: 61%

Observation of Self-Binding in MonolayerHe3

et al. 2012

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We report clear experimental signatures of the theoretically unexpected gas-liquid transition in the first three monolayers of 3 He adsorbed on graphite. The transition is inferred from the linear density dependence of the γ-coefficient of the heat capacity measured in the degenerate region (2 ≤ T ≤80 mK) below a critical liquid density (ρc0). Surprisingly, the measured ρc0 values (0.6∼0.9 nm −2 ) are nearly the same for all these monolayers in spite of their quite different environments. We conclude that the ground-state of 3 He in strict two dimensions is not a dilute quantum gas but a self-bound quantum liquid with the lowest density ever found. PACS numbers: 67.30.hr, 67.30.ej, 67.10.Db, 67.30.ef Matter can in principle be in either gas or a liquid phase at absolute zero if the quantum parameter, the zero-point kinetic energy divided by the potential energy, is large enough. The two-dimensional (2D) helium-3 ( 3 He) system has long been thought as the only material which stays gaseous at the ground state [1]. This system is experimentally realized in 3 He monolayers adsorbed on an atomically flat and strongly attractive graphite surface. Most previous theories based on the variational calculations [2-4], the diffusion Monte Carlo calculation [5] and the Fermi hypernetted chain method [6] support the absence of self-binding of 3 He in 2D. Indeed, no signature of the gas-liquid (G-L) transition was experimentally observed in the first and second layer 3 He on graphite down to T ≈ 3 mK and to areal density ρ = 1 nm −2 [7]. This is in sharp contrast to monolayer 4 He with smaller quantum parameter on graphite. It is well established experimentally [8] and theoretically [9] that in this system the G-L transition takes place at temperatures below 1 K and the self-bound liquid density at T = 0 (ρ c0 ) is 4 nm −2 .The first experimental address to this problem was made by Bhattacharyya and Gasparini [10], who found a kink or small discontinuity near 100 mK in the heat capacity (C) of submonolayer 3 He floated on a thin superfluid 4 He film adsorbed on a Nuclepore substrate. They attributed this to a puddle formation of 3 He in 2D. It is to be noted, however, that in this system the indirect 3 He-3 He interaction mediated by ripplons in the underlying 4 He film, which is not considered in most theoretical works, might be important. In addition, Nuclepore is believed to be a much less uniform substrate than graphite.Recently, Sato et al. [11] found the G-L transition with ρ c0 ≈ 1 nm −2 in the heat-capacity measurements on the third layer of 3 He on graphite down to T = 1 mK. This was inferred from a linear ρ−dependence of γ, the coefficient of the leading T -linear term of C in the degenerate region, as well as a kink at γ ≈ γ ideal . Here2 ) is the γ value of an ideal Fermi gas spreading over the whole surface area (A) of the substrate, and m is the bare mass of 3 He. Note that γ depends only on A and m not on the number of particles in the 2D case. One possible explanation for their result, which contradicts exi...

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Ordering and Phase Transitions in Adsorbed Monolayers of Diatomic Molecules

Marx

Wiechert

1996

Advances in Chemical Physics

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Phases ofHe3andHe4Monolayer Films Adsorbed on Basal-Plane Orien

Cited by 436 publications

References 78 publications

Probing the helium-graphite interaction

Probing the helium-graphite interaction

Observation of Self-Binding in MonolayerHe3

Ordering and Phase Transitions in Adsorbed Monolayers of Diatomic Molecules

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