(1) Istituto Nazionale per la Fisica della Materia, Dipartimento di Fisica, Universita' di Roma Tor Vergata, Via della Ricerca Scientifica, 1-00133 Roma, Italy, IT
Abstract:
We show that different non-conventional superconductors have one fundamental feature in common: pair eigenstates of the Hamiltonian
are repulsion-free, the W = 0 pairs. In extended Hubbard models, pairing can occur for reasonable parameter values. For (N, N) nanotubes the binding energy of the pair depends strongly on the filling and decreases towards a reduced but nonzero value
for the graphite sheet N → ∞.
Received 13 July 2002 Published online 29 November 2002