Superconductivity due to spin fluctuations originating from multiple Fermi surfaces in a double chain superconductor Pr$_2$Ba$_4$Cu$_7$O$_{15-\delta}$}

TL;DR

This paper investigates the mechanism of superconductivity in Pr$_2$Ba$_4$Cu$_7$O$_{15-}$ using a double chain model, revealing spin fluctuation-driven pairing from multiple Fermi surfaces consistent with experiments.

Contribution

It introduces a quasi-one dimensional double chain model with specific interactions and applies the fluctuation exchange method to explain superconductivity in the compound.

Findings

Superconductivity is driven by spin fluctuations from multiple Fermi surfaces.

The superconducting gap has an extended s-wave-like symmetry.

Results align with experimental doping dependence and temperature behavior.

Abstract

The mechanism of superconductivity in Pr$_2$Ba$_4$Cu$_7$O$_{15-\delta}$ is studied using a quasi-one dimensional double chain model with appopriate hopping integrals, on-site $U$, and off-site repulsion $V_1$. Applying the fluctuation exchange method to this model and solving the Eliashberg equation, we obtain the doping dependence of superconductivity that is consistent with the experiments. The superconducting gap has an extended s-wave-like form, which gives a temperature dependence of the spin lattice relaxation rate that does not contradict with the experimental results.