Magnetosensitivity in dipolarly-coupled three-spin systems

TL;DR

This paper demonstrates that dipolar interactions in three-spin systems can produce magnetic field effects on chemical reactions, offering an alternative to hyperfine interactions and broadening understanding of magnetoreception and quantum sensing.

Contribution

It introduces a model showing dipolar interactions can induce magnetosensitivity in three-spin systems, expanding the mechanisms beyond hyperfine interactions.

Findings

Directional sensitivity to weak magnetic fields.

Reaction yield exhibits spikes as a function of magnetic field.

Effects can be tuned by exchange interactions.

Abstract

The Radical Pair Mechanism is a canonical model for the magnetosensitivity of chemical reaction processes. The key ingredient of this model is the hyperfine interaction that induces a coherent mixing of singlet and triplet electron spin states in pairs of radicals, thereby facilitating magnetic field effects (MFEs) on reaction yields through spin-selective reaction channels. We show that the hyperfine interaction is not a categorical requirement to realize the sensitivity of radical reactions to weak magnetic fields. We propose that, in systems comprising three instead of two radicals, dipolar interactions provide an alternative pathway for MFEs. By considering the role of symmetries and energy level crossings, we present a model that demonstrates a directional sensitivity to fields weaker than the geomagnetic field and remarkable spikes in the reaction yield as a function of the magnetic field intensity; these effects can moreover be tuned by the exchange interaction. Our results further the current understanding of the effects of weak magnetic fields on chemical reactions, could pave the way to a clearer understanding of the mysteries of magnetoreception and other biological MFEs and motivate the design of quantum sensors. Further still, this phenomenon will affect spin systems used in quantum information processing in the solid state and may also be applicable to spintronics.