Researchers at Japan's RIKEN Center for Emergent Matter Science have pioneered a method to carve three-dimensional nanoscale devices from single crystals using focused ion beams. By shaping helical structures from a magnetic crystal, they created switchable diodes that direct electricity preferentially in one direction. This geometric approach could enable more efficient electronics.
The breakthrough, detailed in a study published in Nature Nanotechnology in 2026, involves precision sculpting with a focused ion beam to remove material at sub-micron scales. Scientists fabricated microscopic helices from the topological magnetic crystal Co₃Sn₂S₂, composed of cobalt, tin, and sulfur. These tiny structures exhibit nonreciprocal electrical transport, acting as diodes where current flows more easily in one direction than the reverse.
Experiments revealed that the diode effect stems from uneven electron scattering along the chiral, curved walls of the helices. The behavior can be toggled by altering the material's magnetization or the helix's handedness. Additionally, strong electrical pulses were shown to reverse the structure's magnetization, highlighting bidirectional interactions between shape, electricity, and magnetism.
This technique overcomes limitations of traditional fabrication, which often degrade material quality or restrict options. By enabling 3D designs from nearly any crystalline material, it promises smaller, more powerful devices for applications like AC/DC conversion, signal processing, and LEDs.
Max Birch, the study's lead author, explained: "By treating geometry as a source of symmetry breaking on equal footing with intrinsic material properties, we can engineer electrical nonreciprocity at the device level. Our newly developed focused ion beam nanosculpting method opens up a wide range of studies on how three dimensional and curved device geometries can be used to realize new electronic functions."
Group leader Yoshinori Tokura added: "More broadly, this approach enables device designs that combine topological or strongly correlated electronic states with engineered curvature in the ballistic or hydrodynamic transport regime. The convergence of materials physics and nanofabrication points to functional device architectures with potential impact on memory, logic, and sensing technologies."
The findings underscore how physical form can directly manipulate electron motion, paving the way for geometry-driven innovations in electronics.
