Quantitative nanoscale vortex-imaging using a cryogenic quantum magnetometer

TL;DR

This paper demonstrates nanoscale magnetic imaging of vortices in a superconductor using a quantum sensor, providing quantitative insights into superfluid densities and vortex behavior at cryogenic temperatures.

Contribution

It introduces a method for quantitative, nanoscale magnetic imaging of vortices in superconductors with a single NV center sensor, achieving high spatial resolution and model agreement.

Findings

Quantitative imaging of Pearl vortices in YBCO superconductors.

Observation of deviations from monopole approximation in vortex stray fields.

Accurate measurement of local London penetration depth.

Abstract

Microscopic studies of superconductors and their vortices play a pivotal role in our understanding of the mechanisms underlying superconductivity. Local measurements of penetration depths or magnetic stray-fields enable access to fundamental aspects of superconductors such as nanoscale variations of superfluid densities or the symmetry of their order parameter. However, experimental tools, which offer quantitative, nanoscale magnetometry and operate over the large range of temperature and magnetic fields relevant to address many outstanding questions in superconductivity, are still missing. Here, we demonstrate quantitative, nanoscale magnetic imaging of Pearl vortices in the cuprate superconductor YBCO, using a scanning quantum sensor in form of a single Nitrogen-Vacancy (NV) electronic spin in diamond. The sensor-to-sample distance of ~10nm we achieve allows us to observe striking deviations from the prevalent monopole approximation in our vortex stray-field images, while we find excellent quantitative agreement with Pearl's analytic model. Our experiments yield a non-invasive and unambiguous determination of the system's local London penetration depth, and are readily extended to higher temperatures and magnetic fields. These results demonstrate the potential of quantitative quantum sensors in benchmarking microscopic models of complex electronic systems and open the door for further exploration of strongly correlated electron physics using scanning NV magnetometry.