High Temperature Mixed State $c-$Axis Dissipation in Low Carrier Density $Y_{0.54}Pr_{0.46}Ba_{2}Cu_{3}O_{7-\delta}$

TL;DR

This study investigates out-of-plane dissipation in underdoped YPrBaCuO superconductors near the critical temperature, revealing layer decoupling due to phase fluctuations and discrepancies with theoretical predictions of interlayer Josephson current.

Contribution

It demonstrates that in-plane phase fluctuations decouple layers above Tc and provides experimental data on c-axis dissipation and Josephson current in underdoped cuprates, highlighting deviations from layered superconductor theory.

Findings

Ambegaokar-Halperin relationship describes angular magnetoresistivity well.

Layer decoupling occurs above Tc due to phase fluctuations.

Interlayer Josephson current density is smaller than theoretical predictions.

Abstract

The nature of the out-of-plane dissipation was investigated in underdoped $Y_{0.54}Pr_{0.46}Ba_{2}Cu_{3}O_{7-\delta}$ single crystals at temperatures close to the critical temperature. For this goal, temperature and angle dependent out-of-plane resistivity measurements were carried out both below and above the critical temperature. We found that the Ambegaokar-Halperin relationship [V. Ambegaokar, and B. I. Halperin, Phys. Rev. Lett. \textbf{22}, 1364 (1969)] depicts very well the angular magnetoresistivity in the investigated range of field and temperature. The main finding is that the in-plane phase fluctuations decouple the layers above the critical temperature and the charge transport is governed only by the quasiparticles. We also have calculated the interlayer Josephson critical current density, which was found to be much smaller than the one predicted by the theory of layered superconductors. This discrepancy could be a result of the d-wave symmetry of the order parameter and/or of the non BCS temperature dependence of the c-axis penetration length.