Low-temperature critical current of Y1-xCaxBa2Cu3O7-delta thin films as a function of hole content and oxygen deficiency

TL;DR

This study investigates how hole content and oxygen deficiency affect the low-temperature critical current density in Y1-xCaxBa2Cu3O7-delta thin films, revealing that carrier concentration primarily governs the critical current.

Contribution

It demonstrates that the intrinsic critical current density is mainly determined by hole concentration, independent of oxygen deficiency, and peaks near optimal doping levels.

Findings

Critical current density exceeds 10^7 A/cm^2 above optimal doping.

Maximum Jc0 occurs at hole concentration p ~ 0.185.

Oxygen disorder has a secondary effect on critical current.

Abstract

The effects of hole content (p) and oxygen deficiency (delta) on the zero-field critical current density, Jc0, were investigated for high-quality c-axis oriented Y1-xCaxBa2Cu3O7-delta (x = 0, 0.05, 0.10, and 0.20) thin films. Ca was used to introduce hole carriers in the CuO2 planes, independent of the oxygen deficiency in the CuO1-delta chains. Low-temperature Jc0(16K) of these films above the optimum doping were found to be high (> 10^7 Amp/cm^2) and were primarily determined by the hole concentration, reaching a maximum at p ~ 0.185+/-0.005, irrespective of oxygen deficiency. This implies that oxygen disorder plays only a secondary role and the intrinsic Jc0 is mainly governed by the carrier concentration and consequently by the superconducting condensation energy which also peaks at p ~ 0.19 where the pseudogap correlation vanishes.