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TUE: Tuesday Contributed Sessions

TUE 12: Quantum Sensing and Decoherence: Contributed Session to Symposium III

TUE 12.7: Talk

Tuesday, September 9, 2025, 15:45–16:00, ZHG105

Direct imaging of magnetotransport at graphene-metal interfaces with a single-spin quantum sensor — •Chaoxin Ding, Marius Palm, Kevin Kohli, and Christian Degen — ETH Zurich, Zurich, Switzerland

Magnetotransport underlines many important phenomena in condensed matter physics, such as the Hall effect and magnetoresistance (MR) effect, and forms the basis for applications in magnetic memories and spintronic devices. Thus far, most magnetotransport studies have been based on bulk resistance measurements, without direct access to the nanoscale spatial transport pattern. Here, we discuss nanoscale quantum imaging of magnetotransport in a monolayer graphene with an embedded metal disc using a scanning nitrogen-vacancy magnetometer. By visualizing the current flow under an out-of-plane magnetic field around 0.5 T, we directly observe Lorentz-force-induced current deflection at the graphene-to-metal interface. As the carrier density in graphene increases, the current flowing through the graphene sheet is enhanced. In addition, we observe that the MR is more prominent in the ambipolar regime compared to the electron- or hole- doped regimes, which can be attributed to the intrinsic MR effect. Finally, we show that spatial current imaging uncovers non-uniform contact resistances along the circular graphene-metal interfaces, which cannot be easily identified by optical, electrical or topographic characterization.

Keywords: Quantum sensing/imaging; Magnetotransport; Graphene-metal interfaces; Scanning nitrogen-vacancy magnetometer