Nonlinear transport signatures of Fermi arcs and Weyl- superconductivity in ion-milled Weyl semimetals

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. In this presentation, we showcase two representative studies enabled exclusively by FIB-fabricated devices. First, we demonstrate Fermi-arc-induced nonreciprocal transport in the Weyl semimetal TaAs. 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. By carefully excluding other mechanisms, this sign-switchable nonreciprocity is proven to be protected by Fermi arcs.Second, we report nonlinear transport signatures of Weyl superconductivity in ion-milled NbAs, where superconductivity is induced by a FIB-milled amorphous Nb layer. Crucially, we observe an upper critical field exceeding the Pauli limit and a striking rotational symmetry reduction from crystalline four-fold to electronic two-fold. Ruling out extrinsic vortex dynamics, these signatures point to a unidirectional finite-momentum pairing state as the most plausible mechanism. This single-material approach establishes a versatile platform for exploring topological superconductivity in quantum matter.

1. D. Li et al., arXiv:2606.17395
2. D. Li et al, submitted.