η-superconductivity in the one-dimensional Penson-Kolb model

Abstract

Using exact Lanczos diagonalizations we have studied in detail the transition into the η-superconducting state in the Penson-Kolb model. We have shown that the transition occurs at any band filling and the critical value W _c varies between W _c ≃ −1:8t at half-filling to W _c ≃ −2t for two particles on the lattice. The transition corresponds to abrupt and drastic change in the ground-state structure. After the transition the contribution of the one-electron band to the ground-state energy is almost suppressed.