Fluctuating exchange interactions enable quintet multiexciton formation in singlet fission

Abstract

Several recent electron spin resonance studies have observed a quintet multiexciton state during the singlet fission process. Here we provide a general theoretical explanation for the generation of this state by invoking a time-varying exchange coupling between pairs of triplet excitons, and subsequently solving the relevant time-varying spin Hamiltonian for a range of transition times. We simulate experimental ESR spectra and draw qualitative conclusions about the adiabatic/diabatic transition between triplet pair spin states.

Singlet fission for quantum information and quantum computing: the parallel JDE model

“…A recent paper that numerically simulates spin dynamics in singlet fission in Ref. 28 makes a similar approximation.…”

“…Within this framework, depends implicitly on integrals over spatial wavefunctions. Akin to electronically nonadiabatic effects in molecules, fluctuations in nuclear coordinates and exciton hopping can make the time-dependent 23 , 28 . These time-dependent parameters can drive transitions between different spin states of the spin-exciton hamiltonian.…”

“…While hamiltonians similar to Eq. ( 6 ) have appeared more recently in literature 14 – 17 , 19 , 28 , 34 , researchers either use approximations that make Eq. ( 6 ) spin-conserving or they analyze it at weak J.…”

“…Reference’s 37 “singlet character” approximation is not spin-conserving, but is only appropriate when the Zeeman term dominates over J . In this theory the initial and final states are adiabatically connected to one another 28 . The theory presented in this manuscript is a nonadiabatic analog that is applicable when J is large.…”

“…Equation ( 6 ) can describe how the unpairing of to independent triplets takes place (Eq. 4 ) 28 . By measuring quantum beats in delayed fluorescence spectra, Ref.…”