Understanding the nature of electronic states requires access to a variety of fundamental observables. Some can be extracted directly from a well designed sample using, resistance and density of states measurements, 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, and thermal sensitivity[] in the the cryogenic temperature range.
Our lab operates three nanoSQUID-on-tip based microscope spanning the 20mK to 7K temperature range with access to vector magnetic field and variable pressure sample environments. Scientific achievements to date using these tools include direct imaging of orbital magnetism in graphene and transition metal dichalcogenide heterostructures [3-5], including the first magnetic imaging of fractional quantum anomalous Hall phases. Ongoing work includes direct imaging of electron flow in strongly correlated electron systems and investigating the nature of heat transport on the nanoscale in superfluid helium.
[1] Vasyukov et al., Nature Nanotechnology 8:639-644 (2013).
[2] Halbertal et al., Nature 539:407-410 (2016).
[3] C. L. Tschirhart et al., Science 372, 1323-1327 (2021).
[4] C. L. Tschirhart et al., Nature Physics (in press, 2023).
[5] E. Redekop et al., Nature (in press).