The vortex depinning transition in untwinned YBaCuO using complex impedance measurements

TL;DR

This study measures the surface impedance of vortex response in untwinned YBaCuO, revealing how a first order transition affects vortex dynamics and electronic states.

Contribution

It provides detailed broadband impedance spectra and links vortex depinning behavior to electronic state changes in YBaCuO.

Findings

Identification of surface pinned vortex lattice response

Extraction of critical current and flux flow resistivity

Evidence of transition affecting vortex electronic states

Abstract

We present surface impedance measurement of the vortex linear response in a large untwinned YBCO crystal. The depinning spectra obtained over a broad frequency range (100 Hz- 30 MHz) are those of a surface pinned vortex lattice with a free flux flow resistivity (two modes response). The critical current in the "Campbell" like regime and the flux flow resistivity in the dissipative regime are extracted. Those two parameters are affected by the first order transition, showing that this transition may be related to the electronic state of vortices.