Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: W=0 Pairing in $(N,N)$ Carbon Nanotubes away from Half Filling   We use the Hubbard Hamiltonian $H$ on the honeycomb lattice to represent the
valence bands of carbon single-wall $(N,N)$ nanotubes. A detailed symmetry
analysis shows that the model allows W=0 pairs which we define as two-body
singlet eigenstates of $H$ with vanishing on-site repulsion. By means of a
non-perturbative canonical transformation we calculate the effective
interaction between the electrons of a W=0 pair added to the interacting ground
state. We show that the dressed W=0 pair is a bound state for resonable
parameter values away from half filling. Exact diagonalization results for the
(1,1) nanotube confirm the expectations. For $(N,N)$ nanotubes of length $l$,
the binding energy of the pair depends strongly on the filling and decreases
towards a small but nonzero value as $l \to \infty$. We observe the existence
of an optimal doping when the number of electrons per C atom is in the range
1.2$\div$1.3, and the binding energy is of the order of 0.1 $\div$ 1 meV.

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The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
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The categories of this paper are: math-ph
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The categories of this paper are: q-bio
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The categories of this paper are: cmp-lg
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The categories of this paper are: astro-ph
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The categories of this paper are: stat
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The categories of this paper are: eess
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The categories of this paper are: mtrl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: q-alg
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The categories of this paper are: physics
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The categories of this paper are: quant-ph