Effect of oxygen-doping on Bi-2223 vortex matter: Crossover from electromagnetic to Josephson interlayer coupling

TL;DR

This study investigates how oxygen doping affects the vortex matter and interlayer coupling in Bi-2223, revealing a crossover from Josephson to electromagnetic coupling near optimal doping, with implications for superconducting properties.

Contribution

It demonstrates the doping-dependent crossover from Josephson to electromagnetic interlayer coupling in Bi-2223, challenging previous assumptions and providing new insights into vortex matter behavior.

Findings

Oxygen doping increases Tc in the overdoped regime.

The Bragg glass phase stability enlarges with higher doping levels.

A crossover from Josephson to electromagnetic coupling occurs near optimal doping.

Abstract

We study the effect of oxygen-doping on the critical temperature, Tc, the vortex matter phase diagram and the nature of the coupling mechanism between the Cu-O layers in the three-layer Bi2Sr2Ca2Cu3O10+delta (Bi-2223) compound. Contrary to previous reports, in the overdoped (OD) regime we do find a variation of Tc with increasing the oxygen partial-pressure of the post-annealing treatment. This variation is less significant than in the bi-layer parental compound Bi-2212 and does not follow the universal Tc vs.delta relation. Magnetic measurements reveal that increasing delta enlarges the field and temperature stability of the Bragg glass phase. These findings imply that the interlayer coupling between Cu-O layers enhances with delta. The anisotropy parameter estimated from directional first-penetration field measurements monotonously decreases from 50 in the underdoped (UD) to 15 in the OD regimes. However, the in-plane penetration depth presents a boomerang-like behaviour with $\delta$, reaching its minimum value close to optimal doping. These two facts lead to a crossover from a Josephson(OD) to electromagnetic(UD)-dominated coupling of adjacent Cu-O layers in the vicinity of optimal doping.