Independent electron approaches fail to model chirality-induced spin selectivity

Almost everything from particles to DNA to spiral galaxies are made of components that can form in two orientations. This phenomenon of handedness, called chirality, has profound effects on how molecules interact with one another, but challenges remain in effectively modeling such molecules. One topic that continues to vex researchers is chirality-induced spin selectivity, in which a molecule’s handedness influences the spin of its electrons.

Jonas Fransson has provided an outline of the current state of theoretical modeling of chirality-induced spin selectivity. Several years of work on independent electron models have failed to reproduce experimental results. Such work, however, underscores the importance of including electron interactions in models.

“One of the most problematic aspects with the chirality-induced spin selectivity effect is that it appears to violate the consensus of many physical phenomena that are described in the literature,” Fransson said. “And rather to conform the observations to the existing theoretical framework, it is necessary to again plough through the basic assumptions underlying what we think we know about these phenomena.”

Central to these discrepancies are the concepts of Onsager reciprocity, which describes the equality of certain ratios between flows and forces where local equilibrium exists in systems out of equilibrium, and time reversal symmetry, the theoretical symmetry of physical laws under the transformation of time reversal.

Fransson hopes his paper stokes further work challenging fundamental assumptions in physics. He next looks to investigate whether spin-interfaces are viable and what their dynamics may be in addition to the role of electron spin in highly non-equilibrium chemical reactions that often are represented with quasi-equilibrium intermediates.

Source: “Should it really be that hard to model the chirality induced spin selectivity effect?,” by Jonas Fransson, APL Computational Physics (2025). The article can be accessed at https://doi.org/10.1063/5.0289548 .