Coexistence of superconductivity and charge density wave in a correlated regime

To investigate the coexistence of superconductivity and charge density wave (CDW) in a correlated regime, we employ the Green’s functions formalism, as well as the Hubbard-I approximation, as a way to introduce the correlations into the problem, in the form of a repulsive Coulomb interaction $U$. In addition, we investigate the effects of second-nearest neighbor hopping $t_1$ on a pure CDW state. The analysis of the results show that, for small values of $t_1$, both CDW and superconducting gaps compete for the same region on the Fermi surface. The increase of $t_1$ decreases the competition and may lead the system to a coexistence regime. Effects of temperature in the coexistence regime, are also investigated.

💡 Research Summary

The paper investigates the interplay between superconductivity (SC) and charge‑density‑wave (CDW) order in a two‑dimensional correlated electron system using a Green’s‑function formalism combined with the Hubbard‑I approximation. The authors start from a single‑band Hubbard model on a square lattice, adding a BCS‑type pairing interaction V and a CDW interaction with nesting vector Q = (π, π). The electronic dispersion includes both nearest‑neighbor hopping t₀ and second‑nearest‑neighbor hopping t₁: εₖ = 2t₀