Exact-diagonalization study on the effect of long-range Coulomb interaction in the two-chain Hubbard model

Abstract
We present exact-diagonalization results clearly indicating that the long-range part of Coulomb interaction does not sweep away the superconducting region of the two-chain Hubbard model driven by the short-range part. When the model contains the nearest-neighbor Coulomb interaction both for the interchain and the intrachain directions, the region of developed superconducting correlations in the ground state is reduced. The CDW correlation is found to increase, intervening with the competition between superconductivity and CDW. When we include the long-range Coulomb interaction of the type of 1/r, the instability to the CDW state weakens with the superconducting region recovered to some extent compared with the above case.
Article Outline

Article Outline

1. Introduction
2. Model and results
2.1. Model and superconducting correlation functions
2.2. Effect of the intrachain nearest-neighbor Coulomb coupling
2.3. Effect of the intrachain and interchain n.n. Coulomb interaction
3. Two-chain Hubbard model including the long-range Coulomb interaction
4. Summary

Acknowledgements
References