Latent-heat and non-linear vortex liquid at the vicinity of the first-order phase transition in layered high-Tc superconductors

TL;DR

This study uses advanced magnetic measurement techniques to clarify the vortex phase diagram in layered high-Tc superconductors, revealing electromagnetic interlayer coupling and a non-linear vortex phase influenced by bulk pinning.

Contribution

It demonstrates the importance of AC magnetic measurements for probing bulk vortex responses and clarifies the nature of interlayer coupling and vortex phases near the first-order transition.

Findings

AC measurements are essential for bulk vortex response analysis.

Electromagnetic coupling dominates across the entire temperature range.

A non-linear vortex phase exists, possibly affected by bulk pinning.

Abstract

In this work we revisit the vortex matter phase diagram in layered superconductors solving still open questions by means of AC and DC local magnetic measurements in the paradigmatic Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ compound. We show that measuring with AC magnetic techniques is mandatory in order to probe the bulk response of vortex matter, particularly at high-temperatures where surface barriers for vortex entrance dominate. From the $T_{\rm FOT}$-evolution of the enthalpy and latent-heat at the transition we find that, contrary to previous reports, the nature of the dominant interlayer coupling is electromagnetic in the whole temperature range. By studying the dynamic properties of the phase located at $T \gtrsim T_{\rm FOT}$, we reveal the spanning in a considerable fraction of the phase diagram of a non-linear vortex phase suggesting bulk pinning might play a role even in the liquid vortex phase.