IMX Seminar Series - Understanding electronic transport through local magnetic measurements

Electric charge can flow in unexpected ways through a sample, in particular in dissipationless conductors. In this talk, I will discuss how we use a local magnetic probe to visualize electronic transport in two different types of dissipationless conductors. First, we study microstructures fabricated from a heavy-fermion superconductor that exhibit an unusual resistive superconducting transition. We show that this behavior is explained by a spatially modulated transition temperature, and we discover that local strain is the cause of the spatial modulation. Second, we visualize how a non-equilibrium current flows in a quantum anomalous Hall insulator by imaging the magnetic field produced by the current. Against the prevalent expectation that the transport current is concentrated along the edges, we find that the current can flow in the interior of the sample within the dissipationless regime.

Links to most relevant papers
https://www.nature.com/articles/s41563-023-01622-0
https://www.science.org/doi/full/10.1126/science.aao6640

Bio: Katja Nowack received her Ph.D. in Physics from Delft University of Technology in 2009, after
completing a “Diplom” in Physics at RWTH Aachen in Germany.  Her PhD work in Lieven Vandersypen’s group focused on the control and read-out of single spins in gate-defined GaAs quantum dots motivated by prospects of spin-based quantum information processing. In 2011 after a short postdoc in Delft, she joined Kathryn Moler’s group at Stanford as a postdoctoral researcher. There she pivoted to scanning probe microscopy and developed an interest in quantum materials. In 2015, she started her own research group at Cornell University focusing on magnetic imaging. Her lab has a broad set of activities ranging from exploring unconventional superconductors, probing magnetic signatures of emergent phenomena to more applied topics such as developing new sensors for imaging and characterizing flux trapping relevant to structures of superconducting digital circuits.