Conditional Enhancement of Radical Pair Dynamics via Chiral State Preparation

TL;DR

This study systematically evaluates the conditions under which chiral-induced spin selectivity (CISS) enhances radical pair magnetic sensitivity, revealing that such enhancements depend on specific internal interaction alignments and molecular geometries.

Contribution

It provides a comprehensive parameter analysis showing that CISS-induced enhancements are conditional and sensitive to internal interactions and nuclear spin configurations.

Findings

CISS effects are not universal amplifiers of magnetic sensitivity.

Enhancements occur under non-collinear internal interactions.

Adding a second nucleus suppresses CISS-induced effects unless specific conditions are met.

Abstract

Chiral-induced spin selectivity (CISS) has been shown to enhance magnetic sensitivity in radical pair mechanism (RPM) models under specific Hamiltonian conditions, yet whether these enhancements persist across a broader parameter space remains untested. We incorporate the CISS effect as a spin-dependent initial state and recombination operator and systematically evaluate the spin dynamics of a model radical pair across a comprehensive parameter sweep of the RPM Hamiltonian. We characterise the orientational response through symmetric and antisymmetric decomposition of the yield distribution under field reversal, providing a direct quantitative signature of CISS-induced symmetry breaking. Our analysis demonstrates that CISS does not function as a generic amplifier of magnetic sensitivity. Claimed enhancements are conditional on the relative alignment of the internal hyperfine and dipolar interaction axes, arising specifically under conditions of non-collinear internal interactions. Extension to a two-nucleus model confirms that these enhancements are sensitive to nuclear spin. CISS-induced effects observed in the single-nucleus model are substantially suppressed when a second collinear nucleus is introduced, with the exception of the hyperfine axis rotation sweep where non-collinear tensor misalignment drives a robust antisymmetric response. These findings indicate that the conditions for CISS-enhanced magnetoreception are more stringent than previously demonstrated, requiring highly ordered and rigid molecular geometries to sustain the effect.