Electrodynamics of the vortex lattice in untwinned YBaCuO by complex impedance measurements

TL;DR

This study uses complex impedance measurements across a broad frequency range to analyze vortex lattice dynamics in untwinned YBaCuO, revealing the irreversibility line, validating vortex models, and identifying flux flow resistivity behavior at the first order transition.

Contribution

It provides a comprehensive characterization of vortex dynamics in YBaCuO without relying on frequency-dependent pinning parameters, confirming the two modes model and revealing new resistivity features.

Findings

Confirmation of the two modes vortex dynamic model

Identification of the irreversibility line without frequency-dependent pinning parameters

Observation of an abrupt loss of pinning and a step in flux flow resistivity at T_m

Abstract

We report complex impedance measurements in an untwinned YBaCuO crystal. Our broad frequency range covers both the quasi static response and the resistive response of the vortex lattice. It allow us to characterize the irreversibility line without the need of any frequency dependent pinning parameters. We confirm the validity of the two modes model of vortex dynamic, and extract both the surface critical current and the flux flow resistivity around the first order transition $T_{m}$. This latter is identified by the abrupt loss of pinning and by an unexpected step of $\rho_{ff}(T)$ at $T_{m}$.