Perturbation Analysis of Superconductivity in the Trellis-Lattice Hubbard Model

Abstract

We investigate pairing symmetry and transition temperature in the trellis-lattice Hubbard model. We solve the Éliashberg equation using the third-order perturbation theory with respect to the on-site repulsion $U$. We find that a spin-singlet state is very stable in a wide range of parameters. On the other hand, when the electron number density is shifted from the half-filled state and the band gap between two bands is small, a spin-triplet superconductivity is expected. Finally, we discuss a possibility of unconventional superconductivity and pairing symmetry in Sr${}_{14-x}$Ca${}_x$Cu${}_{24}$O${}_{41}$.

7pages, 10 figures. To be published in J. Phys. Soc. Jpn