Imaging of sub-$\mu$A currents in bilayer graphene using a scanning diamond magnetometer

Abstract

Nanoscale electronic transport gives rise to a number of intriguing physical phenomena that are accompanied by distinct spatial patterns of current flow. Here, we report on sensitive magnetic imaging of two-dimensional current distributions in bilayer graphene at room temperature. By combining dynamical modulation of the source-drain current with ac quantum sensing of a nitrogen-vacancy center in a diamond probe, we acquire magnetic field and current density maps with excellent sensitivities of 4.6 nT and 20 nA/$\mu$m, respectively. The spatial resolution is 50-100 nm. We further introduce a set of methods for increasing the technique's dynamic range and for mitigating undesired back-action of magnetometry operation on the electronic transport. Current density maps reveal local variations in the flow pattern and global tuning of current flow via the back-gate potential. No signatures of hydrodynamic transport are observed. Our experiments demonstrate the feasibility for imaging subtle features of nanoscale transport in two-dimensional materials and conductors.

9 pages, 5 figures

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• Scanning nitrogen-vacancy magnetometry down to 350mK
• Magnetic field imaging by hBN quantum sensor nanoarray
• Imaging ferroelectric domains with a single-spin scanning quantum sensor
• Scanning nitrogen-vacancy center magnetometry in large in-plane magnetic fields
• Preparation of Metrological States in Dipolar-Interacting Spin Systems
• Minimizing sensor-sample distances in scanning nitrogen-vacancy magnetometry
• Spectrally stable nitrogen-vacancy centers in diamond formed by carbon implantation into thin microstructures
• Machine Learning for Improved Current Density Reconstruction from 2D Vector Magnetic Images
• Multiplexed scanning microscopy with dual-qubit spin sensors
• Bichromatic microwave manipulation of the NV center nuclear spin using transition not detectable via optically detected magnetic resonance
• Scalable, nanoscale positioning of highly coherent color centers in prefabricated diamond nanostructures
• Intermediate diffusive-ballistic electron conduction around mesoscopic defects in graphene