Detection of the Meissner effect with a diamond magnetometer

We examine the possibility of probing superconductivity effects in metal nanoclusters via diamond magnetometry. Metal nanoclusters have been proposed as constitutive elements of high Tc superconducting nanostructured materials. Magnetometry based on the detection of spin-selective fluorescence of nitrogen-vacancy (NV) centers in diamond is capable of nanoscale spatial resolution and could be used as a tool for investigating the properties of single or multiple clusters interacting among each other or with a surface. We have carried out sensitivity estimates and experiments to understand how these magnetometers could be used in such a situation. We studied the behavior of the sensor as a function of temperature and detected the flux exclusion effect in a superconductor by monitoring the [111]-orientation fine structure spectrum in high-NV density diamond. Our results show that phase transitions can be ascertained in a bulk superconductor with this technique while the principal zero field splitting parameter (D) demonstrates a temperature dependence that may require compensation schemes.