Vortex lock-in transition coinciding with the 3D to 2D crossover in YBa2Cu3O7

TL;DR

This study directly detects a vortex lock-in transition in YBa2Cu3O7, coinciding with the 3D to 2D crossover at 76 K, using torque magnetometry on a high-quality crystal, confirming theoretical models for quasi-2D superconductors.

Contribution

First direct observation of vortex lock-in transition in YBa2Cu3O7 near the 3D-2D crossover, validating existing theoretical models despite low anisotropy.

Findings

Lock-in transition observed below 76 K.

Transition coincides with 3D to 2D crossover.

Torque signal matches theoretical predictions.

Abstract

A vortex lock-in transition was directly detected by torque magnetometry in an overdoped YBa2Cu3O7 single crystal of low anisotropy (\approx 7). The locked-in state was observed below the 3D to 2D crossover temperature Tcr = 76 K, independently of extrinsic pinning effects thanks to a high quality clean crystal and the use of a vortex shaking technique. The shape of the torque signal as a function of the angle between the applied magnetic field and the crystallographic c-axis is in very good agreement with the model developped by Feinberg and Ettouhami [Int. J. Mod. Phys. B 7, 2085 (1993)] for quasi-2D superconductors, despite the low anisotropy of the material.