Effects of Interlayer Interaction on the Superconducting State in YBCO

TL;DR

This paper investigates how interlayer interactions influence the superconducting properties of YBCO, showing that such interactions can enhance critical temperature and induce mixed pairing states, with implications for understanding layered high-temperature superconductors.

Contribution

It demonstrates that interlayer interactions universally enhance T_c and induce s+d pairing mixing in YBCO, regardless of interaction sign, within a weak coupling BCS framework.

Findings

Interlayer interaction enhances critical temperature in YBCO.

Sign of interaction affects the phase but not the magnitude of the order parameter.

Interlayer interaction induces s+d pairing mixing in the layers.

Abstract

For a two layer system in a weak coupling BCS formalism any interlayer interaction, regardless of its sign, enhances the critical temperature. The sign has an effect upon the relative phase of the order parameter in each of the two planes but not upon its magnitude. When one of the planes has a dispersion consistent with CuO chains and no intrinsic pairing interaction there is both an enhancement of the critical temperature and an s+d mixing in both layers as the interlayer interaction is increased. The magnetic penetration depth, c-axis Josephson tunneling, density of states and Knight shift are calculated for several sets of model parameters.