Direct determination of the collective pinning radius in high temperature superconductors

TL;DR

This paper introduces a method using silicon micro-oscillators to directly measure the collective pinning radius in high-temperature superconductors, revealing size-dependent effects on vortex lattice behavior.

Contribution

A novel experimental approach to directly determine the three-dimensional weak collective pinning Larkin radius in high-temperature superconductors.

Findings

Irreversibility line depends on sample size and temperature.

Size-dependent irreversibility line corresponds to crossover in vortex lattice regimes.

Method enables direct measurement of the Larkin radius.

Abstract

We study finite-size effects at the onset of the irreversible magnetic behaviour of micron-sized Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ single crystals by using silicon micro-oscillators. We find an irreversibility line appearing well below the thermodynamic Bragg-glass melting line at a magnetic field which increases both with increasing the sample radius and with decreasing the temperature. We show that this size-dependent irreversibility line can be identified with the crossover between the Larkin and the random manifold regimes of the vortex lattice transverse roughness. Our method allows to determine the three-dimensional weak collective pinning Larkin radius in a {\it direct way}.