Quantum sensing with a SQUID-on-tip scanning probe
Martino Poggio
Department of Physics, University of Basel, Switzerland
Building on the pioneering work of the Zeldov group (Weizmann Institute), we now produce and employ state-of-the-art SQUID-on-tip (SOT) as magnetic scanning probes in our lab in Basel. These devices, which feature a nanometer-scale SQUID on the apex of a sharp scanning probe tip, have magnetic field sensitivities down to 5 nT/Hz1/2, spatial resolutions better than 50 nm, and unmatched thermal sensitivities down to 1 μK/Hz1/2. I will present experiments on both magnetic and superconducting systems, in which these scanning probes are used to reveal previously inaccessible physical information.
In particular, I will first discuss their application in mapping the stray magnetic field produced by individual ferromagnetic nanotubes
(FNTs) as a function of applied magnetic field. The images are taken as each FNT is led through magnetic reversal and, when compared to micromagnetic simulations, reveal the magnetization configurations. Second, I will discuss measurements of a chiral spin-ice sample, in which the stray field of the magnetic elements can be directly mapped. Third, I will present first images of superconducting vortices in films of amorphous MoSi, showing both the dynamics and pinning of individual vortices. The prospects of using such scanning probes to study mesoscopic transport systems, including graphene, topological insulators, and two-dimensional electron gases will also be discussed.