Superconductivity in an attractive two-band Hubbard model with second nearest neighbors

This work extends the calculations performed by G. Litak, T. Ord, K. Rage, and A. Vargunin, Physica C 483, 30 (2012), by including second nearest neighbors in an attractive two-orbital Hubbard model. We assumed that both the intra-orbital (U-i,U-j with i = 1, 2) and the inter-orbital Hubbard correlations (U-i,U- j with i not equal j) are negative; namely, U-i,U-j <= 0, for all(i, j). We calculated the T - n phase diagram in the mean-field approximation. For a finite chemical potential xi(0)(1) and a certain second nearest-neighbor parameter t(2) superconductivity develops in two dome-like regions, each of which has its own energy gap. Notoriously, for t(2)/vertical bar t1 vertical bar = 0.70 and xi 0(1)/vertical bar t1 vertical bar = 3 where t(1) is the nearest-neighbor parameter, T-c becomes zero around n = 2.5. (C) 2017 Elsevier B.V. All rights reserved.