Pressure Dependence of the Irreversibility Line in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$:Role of Anisotropy in Flux-Line Formation

TL;DR

This study investigates how applying pressure affects the irreversibility line in a high-temperature superconductor, revealing the role of anisotropy and interplanar coupling in flux-line formation.

Contribution

We introduce a new pressure measurement technique using third harmonic ac susceptibility to study flux motion in superconductors, highlighting pressure's effect on anisotropy and flux-line behavior.

Findings

Pressure increases interplanar coupling significantly.

Lattice spacing influences flux-line irreversibility.

Pressure modifies anisotropy affecting flux motion.

Abstract

One of the important problems of high-temperature superconductivity is to understand and ultimately to control fluxoid motion. We present the results of a new technique for measuring the pressure dependence of the transition to superconductivity in a diamond anvil cell. By measuring the third harmonic of the {\it ac} susceptibility, we determine the onset of irreversible flux motion. This enables us to study the effects of pressure on flux motion. The application of pressure changes interplanar spacing, and hence the interplanar coupling, without significantly disturbing the intraplanar superconductivity. Thus we are able to separate the effects of coupling from other properties that might affect the flux motion. Our results directly show the relationship between lattice spacing, effective- mass anisotropy, and the irreversibility line in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$. Our results also demonstrate that an application of 2.5 GPa pressure causes a dramatic increase in interplanar coupling.