8 research outputs found
Acoustic phonon exchange, attractive interactions, and the Wentzel-Bardeen singularity in single-wall nanotubes
We derive the effective low-energy theory for interacting electrons in
metallic single-wall carbon nanotubes taking into account acoustic phonon
exchange within a continuum elastic description. In many cases, the nanotube
can be described as a standard Luttinger liquid with possibly attractive
interactions. We predict surprisingly strong attractive interactions for thin
nanotubes. Once the tube radius reaches a critical value \AA, the Wentzel-Bardeen singularity is approached, accompanied by strong
superconducting fluctuations. The surprisingly large indicates that this
singularity could be reached experimentally. We also discuss the conditions for
a Peierls transition due to acoustic phonons.Comment: 11 pages, 2 figures, final version to be published in Phys. Rev.
Superconductivity in carbon nanotube ropes
We investigate the conditions in which superconductivity may develop in ropes
of carbon nanotubes. It is shown that the interaction among a large number of
metallic nanotubes favors the appearance of a metallic phase in the ropes,
intermediate between respective phases with spin-density-wave and
superconducting correlations. These arise in samples with about 100 metallic
nanotubes or more, where the long-range Coulomb interaction is very effectively
reduced and it may be overcome by the attractive interaction from the exchange
of optical phonons within each nanotube. We estimate that the probability for
the tunneling of Cooper pairs between neighboring nanotubes is much higher than
that for single electrons in a disordered rope. The effect of pair hopping is
therefore what establishes the intertube coherence, and the tunneling amplitude
of the Cooper pairs dictates the scale of the transition to the superconducting
state.Comment: 12 page
Effect of Peierls transition in armchair carbon nanotube on dynamical behaviour of encapsulated fullerene
The changes of dynamical behaviour of a single fullerene molecule inside an
armchair carbon nanotube caused by the structural Peierls transition in the
nanotube are considered. The structures of the smallest C20 and Fe@C20
fullerenes are computed using the spin-polarized density functional theory.
Significant changes of the barriers for motion along the nanotube axis and
rotation of these fullerenes inside the (8,8) nanotube are found at the Peierls
transition. It is shown that the coefficients of translational and rotational
diffusions of these fullerenes inside the nanotube change by several orders of
magnitude. The possibility of inverse orientational melting, i.e. with a
decrease of temperature, for the systems under consideration is predicted.Comment: 9 pages, 6 figures, 1 tabl