Understanding the nature of electronic states requires access to a variety of fundamental observables. Some can be extracted directly from a well designed sample–resistance and density of states, e.g.–but others require specialized tools. We build and operate nanoSQUID-on-tip microscopes [1] that allow nanoscale mapping of magnetic and thermal properties. These microscopes are based on a superconducting quantum interference device fabricated at the tip of a quartz pipette, and enable world-leading combination of spatial resolution (down to ~40 nm), magnetic sensitivity (a few nT/rtHz), and thermal sensitivity in the the cryogenic temperature range. Results from the Young lab to date include direct imaging of orbital magnetism in graphene heterostructures [2] and unravelling the mechanism for current-induced magnetic switching by intrinsic spin Hall torque in transition metal dichalcogenide moire structures. Ongoing work includes direct imaging of electron flow in a electron fluids and revealing new mechanisms for spin-orbit coupling in strongly correlated electron systems. In addition, we are building new instrumentation that will bring nanoSQUID on tip microscopy to the 20mK regime, using a custom designed dilution refrigerator in which the entire scanning probe microscope is contained in superfluid helium cell.
[1] Vasyukov et al., Nature Nanotechnology 8:639-644 (2013).
[2] C. L. Tschirhart, M. Serlin, AFY et al., Science 372, 1323-1327 (2021).
[3] C. L. Tschirhart, E. Redekop, AFY et al., Nature Physics (in press, 2023).