Generalized Holstein model for spin-dependent electron transfer reaction

TL;DR

This paper extends the Holstein model to include spin effects, providing a microscopic description of electron transfer reactions influenced by magnetic fields, with implications for understanding avian magnetoreception.

Contribution

The authors develop a generalized Holstein model incorporating spin interactions to describe spin-dependent electron transfer reactions at a microscopic level.

Findings

Triplet state reaction rate depends on magnetic field direction.

Singlet state reaction rate is unaffected by magnetic field orientation.

Model offers insights into the microscopic basis of avian compass.

Abstract

Some chemical reactions are described by electron transfer (ET) processes. The underlying mechanism could be modeled as a polaron motion in the molecular crystal-the Holstein model. By taking spin degrees of freedom into consideration, we generalize the Holstein model (molecular crystal model) to microscopically describe an ET chemical reaction. In our model, the electron spins in the radical pair simultaneously interact with a magnetic field and their nuclear-spin environments. By virtue of the perturbation approach, we obtain the chemical reaction rates for different initial states. It is discovered that the chemical reaction rate of the triplet state demonstrates its dependence on the direction of the magnetic field while the counterpart of the singlet state does not. This difference is attributed to the explicit dependence of the triplet state on the direction when the axis is rotated. Our model may provide a possible candidate for the microscopic origin of avian compass.