Tapping-Mode SQUID-on-Tip Microscopy with Proximity Josephson Junctions

Studying nanoscale dynamics is essential for understanding quantum materials and advancing quantum-chip manufacturing. Still, it remains a major challenge to measure nonequilibrium properties such as current and dissipation, and their relationship to structure. Scanning nanoprobes utilizing superconducting quantum interference devices (SQUIDs) are uniquely suited here due to their unparalleled magnetic and thermal sensitivity. Here, we introduce tapping-mode SQUID-on-tip, which combines atomic force microscopy with nanoSQUID sensing. Our probes minimize the nanoSQUID-sample distance, provide in-plane magnetic sensitivity, and operate on realistic, highly corrugated nanostructures. Frequency multiplexing enables simultaneous imaging of currents, magnetism, dissipation, and topography. The large voltage output of our proximity-junction nanoSQUIDs allows us to resolve nanoscale currents as small as 100 nA using a simple four-probe electronic readout. By capturing local magnetic, thermal, and electronic response without external radiation, our technique offers a powerful noninvasive route to study dynamic phenomena in exotic materials and delicate quantum circuits.