Numerical study of spin-dependent transition rates within pairs of dipolar and strongly exchange coupled spins with (s=1/2) during magnetic resonant excitation

TL;DR

This study numerically investigates how dipolar and exchange interactions affect spin-dependent transition rates during magnetic resonance in coupled spin pairs, revealing how these interactions can be distinguished experimentally.

Contribution

It introduces a superoperator Liouville-space formalism to analyze spin-dependent transport and recombination rates influenced by dipolar and exchange couplings during magnetic resonance.

Findings

Multiple nutation frequency components observed at sqrt{2} gamma B_1 when dipolar coupling dominates.

Exchange coupling mainly affects low-frequency nutation components, not the main sqrt{2} gamma B_1 component.

pEDMR and pODMR can differentiate exchange and dipolar interaction strengths experimentally.

Abstract

The effect of dipolar and exchange interactions within pairs of paramagnetic electronic states on Pauli-blockade-controlled spin-dependent transport and recombination rates during magnetic resonant spin excitation is studied numerically using the superoperator Liouville-space formalism. The simulations reveal that spin-Rabi nutation induced by magnetic resonance can control transition rates which can be observed experimentally by pulsed electrically (pEDMR) and pulsed optically (pODMR) detected magnetic resonance spectroscopies. When the dipolar coupling exceeds the difference of the pair partners' Zeeman energies, several nutation frequency components can be observed, the most pronounced at sqrt{2} gamma B_1 (gamma is the gyromagnetic ratio, B_1 is the excitation field). Exchange coupling does not significantly affect this nutation component; however, it does strongly influence a low-frequency component < gamma B_1. Thus, pEDMR/pODMR allow the simultaneous identification of exchange and dipolar interaction strengths.