Enhancement of Pairing Correlation and Spin Gap through Suppression of Single-Particle Dispersion in One-Dimensional Models

Abstract

We investigate the effects of suppression of single-particle dispersion near the Fermi level on the spin gap and the singlet-pairing correlation by using the exact diagonalization method for finite-size systems. We consider strongly correlated one-dimensional models, which have flat band dispersions near wave number k=π/2, if the interactions are switched off. Our results for strongly correlated models show that the spin gap region expands as the single-particle dispersion becomes flatter. The region where the singlet-pairing correlation is the most dominant also expands in models with flatter band dispersions. Based on our numerical results, we propose a pairing mechanism induced by the flat-band dispersion.

5 pages, including 5 eps figures, to appear in J.Phys.Soc.Jpn Vol.69 No.1