Dipolar and Exchange Coupling Between Carrier Pairs in Disordered Semiconductors Undergoing Resonance

Abstract

The effect of dipolar and exchange interactions within pairs of paramagnetic states on spin-dependent transport and recombination rates during magnetic resonance is studied numerically using the superoperator/Liouville-space formalism. The simulations reveal that induced Rabi oscillations control transition rates that are 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 Rabi frequency components are observed, with the most pronounced at $\sqrt{2}\gamma B_1$ (γ 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.

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