Superconductivity due to spin fluctuations originating from multiple Fermi surfaces in the double chain superconductor Pr 2 Ba 4 Cu 7 O 15-δ

摘要: The mechanism of superconductivity in ${\mathrm{Pr}}_{2}{\mathrm{Ba}}_{4}{\mathrm{Cu}}_{7}{\mathrm{O}}_{15\ensuremath{-}\ensuremath{\delta}}$ is studied using a quasi-one-dimensional double chain model with appropriate hopping integrals, on-site $U$, and off-site repulsion ${V}_{1}$. Applying the fluctuation exchange method to this solving Eliashberg's equation, we obtain doping dependence that consistent experiments. superconducting gap has spin singlet symmetry nodes running between disconnected Fermi surfaces, which gives temperature spin-lattice relaxation rate does not contradict experimental results.