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Electrical initialization and readout of triplet excitons generated via room temperature singlet fission
Wagner, Taylor W.
Wagner, Taylor W.
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2024
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Molecular quantum systems are of rapidly growing interest, but there remains an open question as to the optimal choice of organic framework and spin generating mechanism for each specific quantum application. In this work, we outline and test the viability of a room temperature singlet fission system using opto-electronic initialization and readout for use as a generic quantum system with a focus on quantum sensing. The framework of the triplet-charge interaction can be used to probe the spin state of the triplet exciton in the Zeeman basis by producing either scattering or quenching events. Because the ratio of these two events are fundamentally field dependent, the magnetoconductance response of the system constitutes a fast and convenient room temperature ensemble spin readout without the need for bulkier optical probes. Initialization in the short-term is achieved by the inherent spin biasing present in the singlet fission phenomenon in the linear acenes, causing the neutral triplet sublevel to be preferentially populated at steady state. Direct manipulation of the triplet sublevel spins can be achieved by driving the sublevel transitions on resonance with the appropriate microwave-magnetic field in electrically detected magnetic resonance (EDMR) experiments. Incorporating a host-guest architecture of two linear acenes, we were able to successfully drive sublevel transitions as a function of applied field within isolated guest triplet excitons boasting sufficiently low hopping diffusivity. We conclude with predictive simulations of pulsed resonance experiments that would provide indisputable evidence of the governing spin species present, quantify the amount of doublet-triplet coupling, and allow for reasonable measurement of decoherence processes. These ideas present a convincing route for future work, as we have successfully exhibited the first steps of building a functional room temperature quantum system utilizing singlet fission as the spin initialization mechanism and the triplet-charge interaction as the electrical manipulation and readout scheme.
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