Research in high-pressure superconductivity has advanced significantly, with materials exhibiting superconducting properties at increasingly higher temperatures, albeit under extreme pressure conditions. These advancements hold promise for technological applications, but characterizing these materials in high-pressure environments is a considerable challenge. Diamond microscopy with nitrogen-vacancy (NV) centers has emerged as a powerful tool for diagnosing the superconducting properties of these materials, offering unprecedented sensitivity and spatial resolution.

NV centers in diamond act as quantum sensors, enabling the detection of magnetic fields with exceptional precision. This capability is crucial for studying the magnetic response of superconductors, such as the Meissner effect (the expulsion of magnetic fields from within the material) and the formation of magnetic flux vortices in type-II superconductors. By integrating these sensors directly into diamond anvil cells, researchers can perform in situ measurements of the magnetic properties of superconductors under gigapascal pressures, providing detailed information on the superconducting transition and magnetic phases.

This technique not only allows for the identification of the superconducting phase and the determination of the critical temperature (T_c) and critical field (H_c), but also offers the possibility of mapping the spatial distribution of superconducting properties at the nanoscale. The ability to operate at high pressures and low temperatures, coupled with the non-invasiveness of the technique, makes it an indispensable tool for the study of new superconducting materials. The development of this methodology opens new avenues for understanding the fundamental mechanisms of high-pressure superconductivity and for the search for room-temperature superconductors.