Imaging current in semimetals with cryogenic scanning NV magnetometry*

Among their many unique features, Weyl semimetals are predicted to enable complex electron-electron and electron-phonon interactions. Such behavior has been predicted, and recently measured, to induce correlated flow of electrons through the semimetal.
We study the current profile in a tungsten ditelluride flake by imaging the local magnetic field above it using a nitrogen-vacancy (NV) center in a diamond scanning tip. Using coherent quantum sensing, we obtain magnetic field resolution of ~10nT and spatial resolution of ~100nm.
The current pattern we observe differs substantially from that of a normal metal, suggesting correlated flow through the semimetal.