Entangled, Spin-polarized Excitons from Singlet Fission in a Rigid Dimer

TL;DR

This paper demonstrates that a rigid dimer molecule exhibits long-lived, spin-polarized excitons generated via singlet fission, with potential applications in quantum information due to its persistent spin coherences at elevated temperatures.

Contribution

It introduces a new measurement scheme for spin polarization in singlet fission molecules and provides a quantitative theoretical framework for interpreting the spectra.

Findings

Long-lived spin coherences observed at high temperatures.

Nearly pure initial spin states achieved through optical pumping.

A new noise-reduction measurement technique for magnetic resonance spectra.

Abstract

Singlet fission, a process that splits a singlet exciton into a biexciton, has promise in quantum information. We report time-resolved electron paramagnetic resonance measurements on a molecule, TIPS-BP1$'$, designed to exhibit strongly state-selective relaxation to specific magnetic spin sublevels. The resulting optically pumped "spin polarization" is a nearly pure initial state from the ensemble. The long-lived spin coherences modulate the signal intrinsically, allowing a new measurement scheme that substantially removes noise and uncertainty in the magnetic resonance spectra. A nonadiabatic transition theory with a minimal number of spectroscopic parameters allows the quantitative assignment and interpretation of the spectra. The rigid, covalently bound dimer, TIPS-BP1$'$, supports persistent spin coherences at temperatures far higher than those used in conventional quantum hardware.