On-Site Repulsion as the Source of Pairing in Carbon Nanotubes and Intercalated Graphite

TL;DR

This paper proposes that on-site repulsion can lead to pairing in carbon nanotubes and graphite, with pairing mechanisms explained through W=0 pairs in extended Hubbard models, showing dependence on filling and system size.

Contribution

It introduces the concept that on-site repulsion can facilitate pairing via W=0 pairs in extended Hubbard models for carbon-based materials.

Findings

Pair eigenstates are repulsion-free (W=0 pairs).

Pairing depends on filling and decreases with increasing system size.

Binding energy remains nonzero in the graphite limit.

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 resonable 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 $N \to \infty$.