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Strong excitonic coupling in photosynthetic systems is believed to enable efficient light absorption and quantitative charge separation, motivating the development of artificial multi-chromophore arrays with equally strong or even stronger excitonic coupling. However, large excitonic coupling strengths have typically been accompanied by fast non-radiative recombination, limiting the potential of the arrays for solar energy conversion as well as other applications such as fluorescent labeling. Here, we report giant excitonic coupling leading to broad optical absorption in bioinspired BODIPY dyads that have high photostability, excited-state lifetimes at the nanosecond scale, and fluorescence quantum yields of nearly 50%. Through the synthesis, spectroscopic characterization, and computational modeling of a series of dyads with different linking moieties, we show that the strongest coupling is obtained with diethynylmaleimide linkers, for which the coupling occurs through space between BODIPY units with small separations and slipped co-facial orientations. Other linkers allow for broad tuning of both the relative through-bond and through-space coupling contributions and the overall strength of interpigment coupling, with a tradeoff observed in general between the strength of the two coupling mechanisms. These findings open the door to the synthesis of molecular systems that function effectively as light-harvesting antennas and as electron donors or acceptors for solar energy conversion.
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Imaging dynamics of exciton interactions and coupling in transition metal dichalcogenides
We demonstrate coherent coupling between excitons in a MoSe2/WSe2 heterostructure, as well as rapid interlayer electron and hole transfer. We visualize the spatial homogeneity of the coupling in the presence of significant sample inhomogeneities.
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- Award ID(s):
- 2016356
- PAR ID:
- 10343988
- Date Published:
- Journal Name:
- International Conference on Ultrafast Phenomena
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The coupling between ferroelectric and magnetic order provides a powerful means to control magnetic properties with electric fields. In this study, we have investigated the magnetoelectric (ME) coupling in iridate-oxide based superlattices employing first-principles density functional theory (DFT) calculations. In particular, we have investigated several oxide superlattices, including (SrIrO 3 ) 1 –(CaTiO 3 ) 1 (SIO–CTO) and (SrIrO 3 ) 1 –(BaTiO 3 ) 1 (SIO–BTO), with an alternating single layer of SIO and CTO/BTO. We identify a very large ME coupling in SIO–BTO mediated by both lattice and electronic contributions. In comparison, moderate ME coupling constants are found in SIO–CTO. Further electronic and structural analyses reveal that the large ME coupling of SIO–BTO is caused by the large spin–orbit coupling of 5d iridium as well as the significant polarization induced in the SIO–BTO. Interestingly, we find that the ME coupling in SIO–BTO can further be enhanced by modulating epitaxial strain. These results suggest a route to significantly enhance the ME coupling effects, which might be applicable for other materials and practical applications.more » « less
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In hybrid zones, whether barrier loci experience selection mostly independently or as a unit depends on the ratio of selection to recombination as captured by the coupling coefficient. Theory predicts a sharper transition between an uncoupled and coupled system when more loci affect hybrid fitness. However, the extent of coupling in hybrid zones has rarely been quantified. Here, we use simulations to characterize the relationship between the coupling coefficient and variance in clines across genetic loci. We then re-analyze 25 hybrid zone data sets and find that cline variances and estimated coupling coefficients form a smooth continuum from high variance and weak coupling to low variance and strong coupling. Our results are consistent with low rates of hybridization and a strong genome-wide barrier to gene flow when the coupling coefficient is much greater than 1, but also suggest that this boundary might be approached gradually and at a near constant rate over time.more » « less
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Accepted Manuscript1.0
- Conference Paper:
- The DOI is not currently available.
