An international team of researchers, led by Ulsan National Institute of Science and Technology (UNIST), has directly observed how electron spins behave in real space, providing a new understanding of this complex interaction.
The phenomenon where electron spins align in a specific direction after passing through chiral materials is crucial for future spin-based electronics, yet the underlying mechanism has been unclear. The team’s work shows that chiral materials actively change the spin orientation of electrons, overturning the long-held belief that these materials simply filter spins without affecting their direction.
Chirality is a property found in many natural structures, including DNA and helical springs, where an electric current can cause electrons with a certain spin to pass through more easily - a key principle for advanced spintronic devices. To uncover how this actually happens, the researchers focused on two possibilities: that chiral materials either act as spin filters, blocking one spin orientation, or actively realign electron spins according to their structure.
The team conducted experiments using tellurium nanowires, which naturally form helical shapes. They connected these nanowires to graphene electrodes and used specialized microscopy to track electron spins directly. The results were striking: the spin directions in the nanowires and electrodes matched perfectly, meaning the same spin orientation persisted instead of reversing as expected from a simple filtering effect. This strongly supports the view that chiral structures actively manipulate electron spins.
Theoretical calculations further revealed that as electrons pass through the chiral material, they acquire orbital angular momentum aligned with the structure’s handedness. This orbital motion then sets the direction of their spin, linking the material’s chirality directly to the final spin orientation of the electrons.