Focused ion beam (FIB) techniques offer a powerful route to engineer mesoscopic devices from topological semimetals, granting direct access to their exotic surface and bulk states. Here, we present two representative studies enabled exclusively by FIB fabricated devices.

1. We demonstrate Fermi-arcs-induced nonreciprocal transport in the Weyl semimetal TaAs. Using FIB techniques, we fabricated micro-sized devices that enable simultaneous transport measurements on opposing topological surfaces. While linear transport is dominated by bulk conduction, nonlinear measurements uncover distinct surface contributions with opposite signs on the top and bottom surfaces—directly reflecting the predicted chirality reversal of Fermi arcs.

2. We report nonlinear transport signatures of Weyl-superconductivity in ion-milled NbAs. The superconductivity was induced by a FIB-milled amorphous Nb layer. Proximity-induced superconductivity in the bulk is confirmed via nonlinear signals, and the observed violation of the Pauli limit suggests finite-momentum pairing. These results highlight the versatility of FIB-based device engineering in probing quantum materials.