Yanze Wu and Joseph E. Subotnik from the University of Pennsylvania report that when molecular dynamics pass near a conical intersection, even a small amount of spin-orbit coupling can lead to a huge Berry force effect, which dramatically changes the pathway selection. In particular, for a simple radical reaction with two outgoing reaction channels, an exact quantum scattering solution in two dimensions shows that the presence of a significant Berry force can lead to spin selectivity as large as 100%. The results were published in Nature Communications (link).

A reaction channel where spin dictates choice of product.

Electronic spin is one of the most fundamental and profound observables in quantum mechanics, and spin manipulation is an important topic today with various real-life applications, for example, magnetic data storage. We contend the spin polarization originating from nuclear dynamics should have broad implications for a wide range of phenomena, including novel chirality-induced spin selectivity effects, magneto-chemical metal separations reactions, or even organic spintronic devices.

The relevant Berry force (as a function of position) that leads to the spin selection.

The research was funded by the Center for Sustainable Separations of Metals (CSSM), a National Science Foundation (NSF) Center for Chemical Innovation (CCI), grant number CHE-1925708. This research was also supported by University of Pennsylvania.