Quantum phenomena in the radial thermal expansion of bundles of single-walled carbon nanotubes doped with 3He. A giant isotope effect
A.V. Dolbin, V.B. Esel'son, V.G. Gavrilko, V.G. Manzhelii, N.A. Vinnikov, and S.N. Popov
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Lenin Ave., Kharkov 61103, Ukraine
Department of Physics, Umea University, SE - 901 87 Umea, Sweden
Received February 16, 2011
The radial thermal expansion αr of bundles of single-walled carbon nanotubes saturated with 3He up to the molar concentration 9.4% has been investigated in the temperature interval 2.1–9.5 K by high-sensitivity capacitance dilatometry. In the interval 2.1–7 K a negative αr was observed, with a magnitude which exceeded the
largest negative αr values of pure and 4He-saturated nanotubes by three and two orders of magnitude, respectively. The contributions of the two He isotope impurities to the negative thermal expansion of the nanotube bundles
are most likely connected with the spatial redistribution of 4He and 3He atoms by tunneling at the surface and inside
nanotube bundles. The isotope effect turned out to be huge, probably owing to the higher tunneling probability of 3He atoms.
PACS: 64.70.Tg Quantum phase transitions; PACS: 65.40.De Thermal expansion; thermomechanical effects; PACS: 65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc; PACS: 65.80.–g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems.