Direct Validation of Superconductivity through Contact-Free Detection of Persistent Supercurrents Using Room-Temperature Quantum Magnetometry
The accelerated emergence of new materials is driving the search for high temperature superconductors, but rapid experimental validation remains a critical bottleneck, particularly for microscopic samples under high pressure. Here, we demonstrate one-step direct superconductivity validation through room-temperature, contact-free detection of remnant supercurrents. The technique utilizes a cryogen-free optically pumped atomic magnetometer to detect the temperature-dependent magnetic field produced by supercurrents of a superconductor. The superconducting transition is directly identified by the abrupt disappearance of magnetic field from the remnant supercurrent above the transition temperature and the reversal of the supercurrent direction upon reversing the applied magnetic field. Validated on YBCO microcrystals and REBCO tape, this technique detects pico-Tesla magnetic fields from supercurrents induced by the ambient Earth's magnetic field in a millimeter-sized REBCO square disk, as well as from sub-100 micrometer YBCO microcrystals compatible with high-pressure diamond anvil cells. The use of a ferrite flux guide enables sensitive detection from centimeter-scale distances. Requiring no electrical contacts, magnetic coils, or integrated magnetic sensors, this non-invasive, room-temperature platform offers a scalable approach for high-throughput screening and validation of superconductivity.