Role of the inner copper-oxide plane in interlayer Josephson effects in multi-layered cuprate superconductors

TL;DR

This study investigates the unique superconducting properties of triple-layered cuprate Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+eta}$, revealing differences from double-layer cuprates through Josephson junction behavior and phase fluctuation analysis.

Contribution

It demonstrates that the inner copper-oxide plane significantly influences interlayer Josephson effects, highlighting a different superconducting nature in triple-layered cuprates.

Findings

The c-axis Josephson current density depends on outer plane superfluid density.

Inner plane shields capacitive coupling between IJJs.

Superconducting gap and T_c remain unchanged in triple-layered cuprates.

Abstract

We find systematic signatures suggesting a different superconducting nature for a triple-layered cuprate Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+\delta}$ with respect to a double-layer through the properties of intrinsic Josephson junctions (IJJs). Our measurements on the current-voltage characteristics reveal that the $c$-axis maximum Josephson current density is sensitive to the superfluid density in outer planes while the critical temperature and the superconducting gap remain unaffected. Switching dynamics of stacked IJJs exhibit that the fluctuation in gauge-invariant phase difference of an IJJ implies that the inner plane completely shields the capacitive coupling between adjacent IJJs, which is essential for mono- and bilayered cuprates.