Transverse spin scanning relaxometry of a high temperature superconductor

The NV center in diamond has emerged as a versatile nanoscale sensor due to its long spin coherence times and spin-dependent fluorescence response over a wide temperature range. Increasing the coherence lifetime of shallow NVs without loss of sensitivity has been a challenge due to concomitant paramagnetic impurities near the surface. Here, we monitor and spatially map the coherence lifetime of a single NV spin in an all-diamond scanning probe brought in close proximity with a thin film of TBCCO, a high temperature superconductor. We find a heterogeneous response, with some sections of the sample exhibiting accelerated transverse spin relaxation. Remarkably, we also identify regions where the NV coherence lifetime grows, which we attribute to a Meissner-effect-induced cancelation of the environmental spin noise. Through the use of multi-pulse spin control sequences with variable timing, we also extract the spectral response of the superconductor. These observations open intriguing opportunities to engineer shallow NVs with improved spin coherence.