Adsorption of He isotopes on fluorographene and graphane

Fluid and superfluid phases from quantum Monte Carlo calculations

M. Nava, D. E. Galli, Milton Walter Cole, L. Reatto

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Monolayer films on graphite, remarkably diverse examples of two-dimensional matter, are now well understood in terms of semiempirical interactions. We explore the phase behavior of helium films on two variants of graphene: graphane (graphene coated with H, denoted GH) and graphene fluoride (GF). The behaviors predicted with quantum Monte Carlo differ qualitatively from those on graphite because of the different surface composition, symmetry, and spacing of the adsorption sites. On both substrates we find that the analog of the standard √3×√3 R30 - commensurate state on graphite is unstable. Results include a superfluid ground state for 4He and a fluid ground state for 3He, neither of which has been found for the monolayer film on any substrate; these two-dimensional fluids are anisotropic because of the symmetry imposed by the honeycomb lattice of adsorption sites. In the case of 4He on GF the anisotropy is as large as if the superfluid were restricted to move in a multiconnected space, along the bonds of a honeycomb lattice. The superfluid transition temperature at the ground-state density of 4He on GF (GH) is of order 0.25 (1.1) K. At higher coverages both an incommensurate triangular solid and a commensurate state at filling factor 2/7 are found.

Original languageEnglish (US)
Article number174509
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume86
Issue number17
DOIs
StatePublished - Nov 8 2012

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Graphite
Isotopes
Graphene
graphene
isotopes
Adsorption
adsorption
Fluids
fluids
Ground state
fluorides
graphite
Crystal lattices
Fluorides
ground state
Monolayers
Anisotropic fluids
anisotropic fluids
helium film
Crystal symmetry

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

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abstract = "Monolayer films on graphite, remarkably diverse examples of two-dimensional matter, are now well understood in terms of semiempirical interactions. We explore the phase behavior of helium films on two variants of graphene: graphane (graphene coated with H, denoted GH) and graphene fluoride (GF). The behaviors predicted with quantum Monte Carlo differ qualitatively from those on graphite because of the different surface composition, symmetry, and spacing of the adsorption sites. On both substrates we find that the analog of the standard √3×√3 R30 - commensurate state on graphite is unstable. Results include a superfluid ground state for 4He and a fluid ground state for 3He, neither of which has been found for the monolayer film on any substrate; these two-dimensional fluids are anisotropic because of the symmetry imposed by the honeycomb lattice of adsorption sites. In the case of 4He on GF the anisotropy is as large as if the superfluid were restricted to move in a multiconnected space, along the bonds of a honeycomb lattice. The superfluid transition temperature at the ground-state density of 4He on GF (GH) is of order 0.25 (1.1) K. At higher coverages both an incommensurate triangular solid and a commensurate state at filling factor 2/7 are found.",
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Adsorption of He isotopes on fluorographene and graphane : Fluid and superfluid phases from quantum Monte Carlo calculations. / Nava, M.; Galli, D. E.; Cole, Milton Walter; Reatto, L.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 86, No. 17, 174509, 08.11.2012.

Research output: Contribution to journalArticle

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