Nanoscale Imaging of Current Density with a Single-Spin Magnetometer

Abstract

Charge transport in nanostructures and thin films is fundamental to many phenomena and processes in science and technology, ranging from quantum effects and electronic correlations in mesoscopic physics, to integrated charge-or spin-based electronic circuits, to photoactive layers in energy research. Direct visualization of the charge flow in such structures is challenging due to their nanometer size and the itinerant nature of currents. In this work, we demonstrate non-invasive magnetic imaging of current density in two-dimensional conductor networks including metallic nanowires and carbon nanotubes. Our sensor is the electronic spin of a diamond nitrogen-vacancy center attached to a scanning tip. Using a differential measurement technique, we detect DC currents down to a few µA above a baseline current density of ∼ 2 · 10 4 A/cm 2 . Reconstructed images have a spatial resolution of typically 50 nm, with a best-effort value of 22 nm. Current density imaging offers a new route for studying electronic transport and conductance variations in two-dimensional materials and devices, with many exciting applications in condensed matter physics.

Magnetostatic twists in room-temperature skyrmions explored by nitrogen-vacancy center spin texture reconstruction

“…We show that our results are consistent with a previously unobserved twisted structure with vertically evolving chirality and helicity, which is expected from micromagnetic simulations. Our results and methods will be broadly relevant to nanoscale magnetometry and studies of chiral spin textures for room-temperature spintronics applications 6 , 20 , 30 , 31 , for example a recently suggested magnetic bobber structure that can coexist with skyrmion tubes 32 , 33 , as well as imaging of current distributions 34 , 35 in itinerant magnets and magnetic structures in low-dimensional materials 36 . During the review process of this manuscript, we learned of related measurements performed by Legrand and colleagues 37 , which have independently confirmed our conclusions regarding the existence of twisted skyrmionic structures in magnetic multilayers.…”

Quantum sensing

“…Integration of NV centers into scanning probes has enabled imaging of magnetic fields with sub-100 nm resolution, with applications to nanoscale magnetic structures and domains (Balasubramanian et al, 2008;Maletinsky et al, 2012;Rondin et al, 2012), vortices and domain walls (Rondin et al, 2013;Tetienne et al, 2014Tetienne et al, , 2015, superconducting vortices (Pelliccione et al, 2016;Thiel et al, 2016), and mapping of currents (Chang et al, 2017).…”

Robustness of quantized transport through edge states of finite length: Imaging current density in Floquet topological versus quantum spin and anomalous Hall insulators

“…In the latter case, one images magnetic field produced by the current from which one can reconstruct the local current density with ∼μm spatial resolution [27]. Even higher resolution, with reconstructed images having spatial resolution of ∼10 nm, has been achieved by using scanning tip based on electronic spin of a diamond nitrogen-vacancy (NV) center [28][29][30]. Particularly intriguing questions that such images can answer are how electron flux transitions from topologically trivial NM lead present in every experimental device into the region of 2D TI of finite length where the flux is confined within narrow edge currents, as well as how processes at the NM-lead/2D-TI interface affect the total current and the corresponding conductance.…”