Spin-dependent transition rates through exchange coupled localized spin pairs during coherent spin excitation

TL;DR

This paper theoretically investigates how exchange interactions in spin pairs influence spin-dependent transport and recombination during coherent spin excitation, revealing differences between experimental observables and potential for accessing forbidden transitions.

Contribution

It predicts the dominance of beat oscillations over nutations in rate modulation and highlights the potential of pEDMR/pODMR to probe ESR forbidden singlet transitions.

Findings

Beat oscillations dominate rate changes at high exchange or field strengths.

Rate oscillation intensities decrease with increasing exchange.

pEDMR/pODMR can access ESR forbidden singlet transitions.

Abstract

The effect of exchange interactions within spin pairs on spin-dependent transport and recombination rates through localized states in semiconductors during coherent electron spin resonant excitation is studied theoretically. It is shown that for identical spin systems, significant quantitative differences are to be expected between the results of pEDMR/pODMR experiments were permutation symmetry is the observable as compared to pESR experiments with polarization as the observable. It is predicted that beat oscillations of the spin nutations and not the nutations themselves dominate the transport or recombination rates when the exchange coupling strength or the field strength of the exciting radiation exceed the difference of the Zeeman energies within the spin pair. Furthermore, while the intensities of the rate oscillations decrease with increasing exchange within the spin pairs, the singlet and triplet signals retain their relative strength. This means that pEDMR and pODMR experiments could allow better experimental access to ESR forbidden singlet transitions which are hardly or not at all accessible with conventional pulsed electron spin resonance spectroscopy.