Atomic-scale investigation of magnetochiral tunneling effect in chiral-structured Co1/3NbS2

Detecting a magnetic signal in spin-polarized scanning tunneling microscopy (SP-STM) is known to depend on the magnetic order within the subject material, breaking time-reversal symmetry. However, the intricate interplay between electric carriers and crystallographic symmetries unveils intriguing manifestations of magnetoelectric interactions. For instance, a polar structure gives rise to a nonlinear Hall effect, while a chiral structure introduces chirality-induced spin selectivity. In this proof-of-concept study, we explore a novel application of SP-STM to observe magnetic contrast generated by crystallographic chirality on an intercalated transition metal dichalcogenide, Co1/3NbS2. The magnetic signal alternates in contrast around a topological vortex point and the tunneling spectroscopy reverses with the chirality and tunneling direction. We propose that an imbalanced Berry curvature, referred to as a Berry curvature dipole, plays a pivotal role in this novel magnetochiral tunneling effect, as the chiral structure forces a radial texture of Berry curvature in the reciprocal space. The result offers potential applications of the atomic-scale investigation tool in the study of various crystallographic symmetries and Berry curvature textures.