Optical projection and spatial separation of spin entangled triplet-pairs from the S1 (21Ag-) state of pi-conjugated systems
arXiv:2002.12465 · doi:10.1016/j.chempr.2020.09.011
Abstract
The S1 (21Ag-) state is an optically dark state of natural and synthetic pi-conjugated materials that can play a critical role in optoelectronic processes such as, energy harvesting, photoprotection and singlet fission. Despite this widespread importance, direct experimental characterisations of the electronic structure of the S1 (21Ag-) wavefunction have remained scarce and uncertain, although advanced theory predicts it to have a rich multi-excitonic character. Here, studying an archetypal polymer, polydiacetylene, and carotenoids, we experimentally demonstrate that S1 (21Ag-) is a superposition state with strong contributions from spin-entangled pairs of triplet excitons (1(TT)). We further show that optical manipulation of the S1 (21Ag-) wavefunction using triplet absorption transitions allows selective projection of the 1(TT) component into a manifold of spatially separated triplet-pairs with lifetimes enhanced by up to one order of magnitude and whose yield is strongly dependent on the level of inter-chromophore coupling. Our results provide a unified picture of 21Ag-states in pi-conjugated materials and open new routes to exploit their dynamics in singlet fission, photobiology and for the generation of entangled (spin-1) particles for molecular quantum technologies.
arXiv comment37 pages, 6 figures
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- From Non-Markovian Dissipation to Spatiotemporal Control of Quantum Nanodevices
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- How Does the Symmetry of S1 Influence Exciton Transport in Conjugated Polymers?
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