Spin Fine Structure Reveals Biexciton Geometry in an Organic Semiconductor

Yunusova, K. M.; Bayliss, Sam L.; Chanelière, Thierry; Деркач, В. Н.; Anthony, John E.; Chepelianskii, A. D.; Weiss, Leah R.

doi:10.1103/physrevlett.125.097402

Cited by 11 publications

(18 citation statements)

References 37 publications

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“…However, decreasing the exciton density below a certain threshold requires more sensitive methods for spin readout. Enhanced sensitivity may be accomplished by electrically or optically probing the 5 (TT) state, for example by measuring spin-selective rates or yields of photocurrent , or delayed fluorescence, ,, which may be further enhanced by engineering strong light–matter coupling in microcavities. , Emission observed from the TCHS–tetracene crystals (Figure S8) demonstrates promise toward future optical readout.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, the spins of the 5 (TT) state can be addressed and manipulated using pulsed microwaves to execute quantum gate operations, the results of which can be read out using either pulse-EPR or optically detected magnetic resonance (ODMR) spectroscopies. 15,20,30,31 The latter offers the possibility of single spin sensitivity and is possible because decay of the 5 (TT) state via the 1 (TT) state by triplet−triplet annihilation produces delayed fluorescence. The 5 (TT) state is used here to drive single-qubit spin-flip gate operations and may be used in future work to implement two-qubit gate operations.…”

Section: ■ Introductionmentioning

confidence: 99%

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Using Molecular Design to Enhance the Coherence Time of Quintet Multiexcitons Generated by Singlet Fission in Single Crystals

et al. 2022

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Multiexciton quintet states, 5 (TT), photogenerated in organic semiconductors using singlet fission (SF), consist of four quantum entangled spins, promising to enable new applications in quantum information science. However, the factors that determine the spin coherence of these states remain underexplored. Here, we engineer the packing of tetracene molecules within single crystals of 5,12-bis(tricyclohexylsilylethynyl)tetracene (TCHS−tetracene) to demonstrate a 5 (TT) state that exhibits promising spin qubit properties, including a coherence time, T 2 , = 3 μs at 10 K, a population lifetime, T pop , = 130 μs at 5 K, and stability even at room temperature. The single-crystal platform also enables global alignment of the spins and, consequently, individual addressability of the spin-sublevel transitions. Decoherence mechanisms, including exciton diffusion, electronic dipolar coupling, and nuclear hyperfine interactions, are elucidated, providing design principles for increasing T 2 and the operational temperature of 5 (TT). By dynamically decoupling 5 (TT) from the surrounding spin bath, T 2 = 10 μs is achieved. These results demonstrate the viability of harnessing singlet fission to initiate multiple electron spins in a well-defined quantum state for next-generation molecular-based quantum technologies.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Using Molecular Design to Enhance the Coherence Time of Quintet Multiexcitons Generated by Singlet Fission in Single Crystals

et al. 2022

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“…12−14 The quintet ESR signature provides direct experimental evidence for a bound triplet pair state, and the analysis of its ESR spectrum and zero-field-splitting (ZFS) parameters can provide information about the spatial extent and geometry of this state. 15 For high-spin quintet intermediates to persist on the timescale of an ESR experiment without rapidly dephasing, SF chromophores are typically linked to form well-defined dimers or oligomers. 16,17 While this covalent approach does offer tunability and rigid control over geometry, it is synthetically challenging to extend the number of coupled SF chromophores.…”

Section: ■ Introductionmentioning

confidence: 99%

Photogeneration of Spin Quintet Triplet–Triplet Excitations in DNA-Assembled Pentacene Stacks

et al. 2023

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Singlet fission (SF), an exciton-doubling process observed in certain molecular semiconductors where two triplet excitons are generated from one singlet exciton, requires correctly tuned intermolecular coupling to allow separation of the two triplets to different molecular units. We explore this using DNAencoded assembly of SF-capable pentacenes into discrete π-stacked constructs of defined size and geometry. Precise structural control is achieved via a combination of the DNA duplex formation between complementary single-stranded DNA and the local molecular geometry that directs the SF chromophores into a stable and predictable slip-stacked configuration, as confirmed by molecular dynamics (MD) modeling. Transient electron spin resonance spectroscopy revealed that within these DNA-assembled pentacene stacks, SF evolves via a bound triplet pair quintet state, which subsequently converts into free triplets. SF evolution via a long-lived quintet state sets specific requirements on intermolecular coupling, rendering the quintet spectrum and its zero-fieldsplitting parameters highly sensitive to intermolecular geometry. We have found that the experimental spectra and zero-field-splitting parameters are consistent with a slight systematic strain relative to the MD-optimized geometry. Thus, the transient electron spin resonance analysis is a powerful tool to test and refine the MD-derived structure models. DNA-encoded assembly of coupled semiconductor molecules allows controlled construction of electronically functional structures, but brings with it significant dynamic and polar disorders. Our findings here of efficient SF through quintet states demonstrate that these conditions still allow efficient and controlled semiconductor operation and point toward future opportunities for constructing functional optoelectronic systems.

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“…While the two-conformation stochastic model is simple, it allows us to draw qualitative conclusions about how quintet formation rate varies with field direction. This information may be fruitfully coupled with EPR and ODMR experiments, which are able to detect quintet population in a way that is sensitive to field direction [48]. For example, at high field the region of the EPR/ODMR spectrum corresponding to θ = 50 • is predicted here to form quintets more slowly than, say, θ = 70 • .…”

Section: B Magnetic Field Effects On Stochastic Conformational Switchingmentioning

confidence: 97%

Quintet formation and exchange fluctuations: The role of stochastic resonance in singlet fission

Collins¹,

Campaioli²,

Tayebjee³

et al. 2022

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Singlet fission describes the spin-conserving production of two triplet excitons from one singlet exciton. The existence of a spin-2 (quintet) triplet-pair state as a product of singlet fission is well established in the literature, and control of quintet formation is an important step towards applying singlet fission in photovoltaics and quantum information. However, a definitive mechanism for quintet formation is yet to be established, which makes it difficult to design materials for optimal quintet formation. Here we outline a mechanism in which inter-triplet exchange coupling fluctuations drive fast and efficient quintet formation. In contrast with conventional wisdom, we show that quintet population can arise despite strong exchange coupling. We evaluate the performance of this quintet formation mechanism in two regimes of conformational freedom, and relate quintet dynamics to material properties of singlet fission molecules.

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Spin Fine Structure Reveals Biexciton Geometry in an Organic Semiconductor

Cited by 11 publications

References 37 publications

Using Molecular Design to Enhance the Coherence Time of Quintet Multiexcitons Generated by Singlet Fission in Single Crystals

Using Molecular Design to Enhance the Coherence Time of Quintet Multiexcitons Generated by Singlet Fission in Single Crystals

Photogeneration of Spin Quintet Triplet–Triplet Excitations in DNA-Assembled Pentacene Stacks

Quintet formation and exchange fluctuations: The role of stochastic resonance in singlet fission

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