Tapping-mode SQUID-on-tip Microscopy with Proximity Josephson Junctions

TL;DR

This paper introduces a novel tapping-mode SQUID-on-tip microscopy technique that combines AFM with nanoSQUID sensing, enabling high-sensitivity, non-invasive imaging of nanoscale currents, magnetism, and dissipation in quantum materials.

Contribution

It presents a new proximity-junction nanoSQUID probe integrated with AFM that operates without lasers and allows simultaneous multi-parameter imaging at the nanoscale.

Findings

Able to resolve currents as small as 100 nA

Operates without external radiation or cryogenic amplification

Enables non-invasive, multi-parameter imaging of quantum materials

Abstract

Studying nanoscale dynamics is essential for understanding quantum materials and advancing quantum chip manufacturing. Still, it remains a major challenge to measure non-equilibrium properties such as current and dissipation, and their relation 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 (AFM) with nanoSQUID sensing. Our probes minimize nanoSQUID-sample distance, provide in-plane magnetic sensitivity, and operate without lasers. 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 without cryogenic amplification. By capturing local magnetic, thermal, and electronic response without external radiation, our technique offers a powerful non-invasive route to study dynamic phenomena in exotic materials and delicate quantum circuits.