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The discovery of high-Tc superconductivity with Tc =
15K in 4 angstrom single-walled carbon nanotubes (
SWNT's) [1] has greatly stimulated the investigation
of new mechanisms of superconductivity, and the
formulation of adequate low-dimensional models of
strongly correlated electron systems. This result,
which is comparable to the epoch-making Muller-Bednorz
discovery of high-Tc superconductivity in cuprates,
leads to a key question about the nature of a
mechanism of high-Tc superconductivity in SWNT's,
namely: How can a superconducting state be realized
with strong repulsive electron-electron interaction in
low-dimensional systems such as SWTN's?
A two-band fermion model with boundary fields
describing the band structure of SWNT is proposed and
solved exactly by the nested Bethe ansatz [2].
The fermions, occupying two degenerated subbands that
are shifted relative to each other, interact via
nner- and inter-band on-site Coulomb interactions, and
one-particle and correlated on-site hybridizations.
The critical exponents of the correlation functions
are calculated using the Bethe ansatz solution and
conformal field theory. It is found that a two
component electron liquid state, one of which is
defined by an attractive effective
electron-electron interaction, is realized for strong
hybridized interaction. The attractive interaction
leads to the formation of a spinless bound state of
Cooper-type pairs and dominating correlations of
singlet pairs for arbitrary band-fillings. We suggest
that this electron pairing mechanism may be the key to
resolving the nature of superconductivity in SWNT's.
1. Z.K. Tang et al., Science 292, 2462 (2001). 2. Igor N.Karnaukhov and Cees G.H.Diks, Hybridized mechanism of pairing of fermions in single-walled carbon nanotubes, Phys. Rev. B, v.74, 235432 (2006). |
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