Imaging quantum materials with scanning SQUID microscopy

Competition or cooperation between different electronic orders with similar energy scales often gives rise to new or unexpected behaviors. Detecting traces of such orders requires versatile probes, which can probe different aspects of the system, such as conductivity, superconductivity and magnetism. In my talk, I will describe a few systems where our local view uncovered surprising mesoscopic effects. I will focus on two polymorphs of a van-der Waals material, 4Hb-TaS2, in which we found a hidden magnetic phase, revealed by spontaneous vortices hosted by the superconductor, and 1T- TaS2, a switchable charge-density-wave system in which we found a surprising rearrangement of current flow. Overall, our results highlight the power of scanning SQUID microscopy in probing the properties of quantum materials and providing local insights into their behavior.