Direct detection of scalar spin chirality via nonreciprocal transport in CoTa₃S₆

Electrons moving through non-trivial spin textures pick up a Berry phase, effectively experiencing an emergent gauge field, giving rise to the topological Hall effect (THE). In CoTa₃S₆, scalar spin chirality induced THE has been discovered, but it probes the emergent gauge field rather than the chirality itself. We report a direct, symmetry-based detection of chirality in CoTa₃S₆ using nonreciprocal (diode-like) transport. We FIB-carve macroscopically achiral devices from single crystals to remove geometric artifacts, ensuring any chiral transport originates intrinsically.

In our research, the nonreciprocal transport signals form a clear hysteresis loop under magnetic-field sweeps, showing that the global chirality can be switched by field and remains when the field returns to zero. Importantly, the nonreciprocal signal tracks the Hall response: its sign and field dependence changes simultaneously with the THE, demonstrating the correspondence between the chirality and the gauge field. Interestingly, the longitudinal magnetoresistance exhibits a large chirality response at a given field, providing strong contrast between opposite chiral states and enabling simple two-terminal readout. We also demonstrate current-pulse control to write and erase the chiral states.

Our results establish nonreciprocal transport as a practical, direct probe of scalar spin chirality and identify CoTa₃S₆ as a platform for chirality-based antiferromagnetic memory with low stray field.