Magnetochiral Spin-Polarized Tunneling in a Paramagnetic State

Crystallographic chirality can mediate various optical and electrical magnetochiral effects. Since these effects have been studied in bulk optical, transport or non-local probe setups, investigation with a local probe is necessarily the next step towards further understanding of the intriguing phenomena closer to the quantum regime. We observed a spin-polarized scanning tunneling microscopy (SP-STM) contrast in the chiral domains of Co1/3NbS2 in a paramagnetic state, which is unexpected in the conventional SP-STM mechanism. This spin-polarized tunneling, depending on the local structural chirality, is argued to be an inverse magnetochiral effect due to a dynamic coupling between tunneling electrons and chirality. In addition, using the standard STM, we also find magnetochiral nonreciprocal tunneling in the presence of external magnetic fields, considered as the inverse process. Our results demonstrate a new application of SP-STM in detecting the dynamic interaction of tunneling electrons with broken crystallographic symmetries.