Mechanics of Individual, Isolated Vortices in a Cuprate Superconductor

TL;DR

This study uses magnetic force microscopy to image and manipulate individual vortices in a cuprate superconductor, revealing unexpected responses and pinning behaviors related to microscopic defects.

Contribution

It provides direct measurements of single vortex interactions with disorder, highlighting new effects in vortex dynamics and pinning in high-temperature superconductors.

Findings

Enhanced vortex response to transverse wiggle

Anisotropic vortex pinning indicating oxygen vacancy clustering

Demonstration of MFM's capability to probe microscopic vortex-defect interactions

Abstract

Superconductors often contain quantized microscopic whirlpools of electrons, called vortices, that can be modeled as one-dimensional elastic objects. Vortices are a diverse playground for condensed matter because of the interplay between thermal fluctuations, vortex-vortex interactions, and the interaction of the vortex core with the three-dimensional disorder landscape. While vortex matter has been studied extensively, the static and dynamic properties of an individual vortex have not. Here we employ magnetic force microscopy (MFM) to image and manipulate individual vortices in detwinned, single crystal YBa2Cu3O6.991 (YBCO), directly measuring the interaction of a moving vortex with the local disorder potential. We find an unexpected and dramatic enhancement of the response of a vortex to pulling when we wiggle it transversely. In addition, we find enhanced vortex pinning anisotropy that suggests clustering of oxygen vacancies in our sample and demonstrates the power of MFM to probe vortex structure and microscopic defects that cause pinning.