Nanosculpted 3D helices of a magnetic Weyl semimetal with switchable non-reciprocal electron transport

The emergent properties of materials are governed by the symmetries of their underlying atomic, spin and charge order. Therefore, intrinsic material properties usually constrain the exploration of symmetry-breaking effects. Focused ion beam (FIB) fabrication now enables the structuring of bulk crystals into ultraprecise transport devices, allowing the study of geometrical symmetry breaking on mesoscopic length scales. Here we extend FIB nanostructuring into three-dimensional, curvilinear geometries. Using single crystals of the high-mobility, centrosymmetric magnetic Weyl semimetal Co₃Sn₂S₂, we sculpt helices with lengths of 3-14 μm, diameters of 1-4 μm and pitches ranging from 500 nm to 2 μm. Lock-in measurements on the helical devices at temperatures between 10 K and 190 K show that the combination of imposed inversion symmetry-breaking geometry and ferromagnetism yields non-reciprocal electron transport-or diode effect-at zero applied magnetic field, exceeding classical self-field expectations by orders of magnitude at low temperatures. We attribute this behaviour to the quasi-ballistic motion of carriers as the mean free path approaches the length scale of the chiral device geometry. Finally, we show that current pulses can switch the magnetization of the device. These results highlight the potential of FIB nanosculpting to engineer symmetry and functionality beyond conventional device geometries.