One-dimensional and two-dimensional quantum systems on carbon nanotube bundles
ABSTRACT We report the first measurement of the structure of 4He atoms adsorbed on bundles of single-walled carbon nanotubes. Neutron diffraction techniques and nanotube samples closed at the end were used. At low coverage, 4He forms a 1D, single line lattice along the grooves between two nanotubes on the surface of the nanotube bundles. As coverage is increased, additional lines of 1D lattices form along the grooves. This is followed by an incommensurate, 2D monolayer covering the whole nanotube bundle surface. The lattice constants of these 1D and 2D systems are largely independent of filling once a single 1D line is formed. No occupation of the interstitial channels between nanotubes is observed in the present sample.
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ABSTRACT: The path-integral Monte Carlo method has been employed to study local superfluidity of 4He layers adsorbed on a C20 molecular surface. Strong inhomogeneity in the superfluid response between the first two helium layers around the fullerene molecule is found. Furthermore we find that even the strongly-bound first layer exhibiting a clear structural order has a finite superfluid fraction when the second layer is filled with itinerant helium atoms. This first-layer superfluidity is understood to be due to exchange coupling mediated by the second-layer helium atoms.Journal- Korean Physical Society 01/2012; 60(1). DOI:10.3938/jkps.60.14 · 0.43 Impact Factor
Article: Adsorption on the carbon nanotubes[Show abstract] [Hide abstract]
ABSTRACT: Adsorption on single walled carbon nanotubes (SWCNTs) is a subject of growing experimental and theoretical interest. The possible adsorbed patterns of atoms and molecules on the single-walled carbon nanotubes vary with the diameters and chirality of the tubes due to the confinement. The curvature of the carbon nanotube surface enlarges the distance of the adsorbate atoms and thus enhances the stability of high coverage structures of adsorbate. There exist two novel high-coverage stable structures of potassium adsorbed on SWCNTs, which are not stable on graphite. The electronic properties of SWCNTs can be modified by adsorbate atoms and metal-semiconductor and semiconductor-semi-conductor transitions can be achieved by the doping of alkali atoms.Frontiers of Physics in China 09/2006; 1(3). DOI:10.1007/s11467-006-0019-7 · 1.44 Impact Factor
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ABSTRACT: We have performed path-integral Monte Carlo calculations to study the adsorption of N 4He atoms on a single C28 fullerene molecule. Radial density distributions show a layer-by-layer growth of 4He with the first adlayer being located at a distance of 5.3 Å from the center of C28. The monolayer is found to show a commensurate structure at N=16 with each of the 16 adsorption sites on the molecular surface being occupied by one 4He atom. As more helium atoms are adsorbed beyond N=16, the adlayer is in a mixed state consisting of 4 localized atoms at the hexagonal faces and the other atoms delocalized over the pentagonal faces. Another structurally-ordered state is observed at N=32, where the helium layer shows the same crystalline structure with an icosahedral symmetry as observed for 32 4He atoms on a C60 molecule. It is found that more 4He atoms can be squeezed into the first layer to disrupt this icosahedral structure when enough 4He atoms are added in the second layer. Finally we observe the reentrant superfluid response of the monolayer with superfluidity being quenched completely at the ordered states of N=16 and 32.Journal of Low Temperature Physics 06/2012; 171(5-6). DOI:10.1007/s10909-012-0732-2 · 1.04 Impact Factor