Laser Modulation of Superconductivity in a Cryogenic Wide-field Nitrogen-Vacancy Microscope

TLDR

The study develops a cryogenic wide‑field nitrogen‑vacancy microscope to image Abrikosov vortices and transport currents in a superconducting Nb film. The microscope, operating at 4 K, uses NV centers to capture magnetic field maps of the Nb film, revealing vortex and current distributions. They observed that higher laser power quenches vortices while lower power causes them to cluster at hot spots, with temperature gradients across the film directing current paths even in the fully superconducting phase, and demonstrated that low‑power NV imaging can resolve mesoscopic superconducting phenomena at 4 K with sub‑micrometer resolution.

Abstract

We realize a cryogenic wide-field nitrogen-vacancy microscope and use it to image Abrikosov vortices and transport currents in a superconducting Nb film. We observe the disappearance of vortices upon increase of laser power and their clustering about hot spots upon decrease, indicating local quenching of superconductivity by the laser. Resistance measurements confirm the presence of large temperature gradients across the film. We then investigate the effect of such gradients on transport currents where the current path is seen to correlate with the temperature profile even in the fully superconducting phase. In addition to highlighting the role of temperature inhomogeneities in superconductivity phenomena, this work establishes that under sufficiently low laser power conditions wide-field nitrogen-vacancy microscopy enables imaging over mesoscopic scales down to 4 K with submicrometer spatial resolution, providing a new platform for spatially resolved investigations of a range of systems from topological insulators to van der Waals ferromagnets.