从第一性原理理解分子光激发三重态的自旋相干性
Understanding the spin coherence of molecular photoexcited triplet states from first principles
- James Watt School of Engineering, University of Glasgow（格拉斯哥大学詹姆斯·瓦特工程学院）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
该研究从第一性原理系统探索了并五苯-对三联苯体系中光激发三重态的自旋退相干机制，揭示了零场与高场下不同核的驱动作用及零场分裂参数对相干时间的延长效应，为分子自旋量子探针的设计提供理论指导。
AI中文摘要：
光学可读的分子自旋因其纳米尺度的模块化、合成可调性以及灵敏读出的潜力，作为量子传感器颇具吸引力。特别是，有机分子中的光激发自旋三重态在室温下支持高光学-自旋对比度方面令人关注。其效用以其相干性为基础，这需要对相干性进行详细理解。在此，我们从第一性原理出发，系统地探索了室温光学检测自旋相干性的基准分子系统——与对三联苯宿主耦合的并五苯客体分子——的Hahn回波退相干。利用广义簇关联展开方法，我们研究了从零场到高磁场下核自旋诱导退相干的机制，探讨了客体与宿主分子、特定核、零场分裂相互作用以及超精细参数的作用。我们描述了零场退相干如何由客体上的约6个核驱动，而高场退相干由宿主中的约600个核驱动；纵向零场分裂参数$D$如何延长$T_2$；以及驱动退相干的磁场依赖过程。这些结果推进了我们对光学可读分子自旋中退相干的理解，为其合成增强和作为量子探针的部署提供了见解。
英文摘要：
Optically readable molecular spins are attractive as quantum sensors due to their nanoscale modularity, synthetic tunability, and scope for sensitive readout. In particular, photoexcited spin-triplet states in organic molecules are appealing in supporting high optical-spin contrast at room temperature. Their utility is underpinned by their coherence, which warrants a detailed understanding of it. Here, from first principles, we systematically explore the Hahn-echo decoherence of the benchmark molecular system for room-temperature optically detected spin coherence---pentacene guest molecules coupled to a para-terphenyl host. Using generalized cluster-correlation expansion methods, we investigate the mechanisms of nuclear-spin-induced decoherence from zero to high magnetic field, exploring the role of guest vs host molecules, specific nuclei, zero-field splitting interactions, and hyperfine parameters. We describe how zero-field decoherence is driven by ~6 nuclei on the guest, while high-field decoherence is driven by ~600 nuclei in the host; how the longitudinal zero-field splitting parameter, $D$, can prolong $T_2$; and the magnetic-field-dependent processes which drive decoherence. These results advance our understanding of decoherence in optically readable molecular spins, providing insight for their synthetic enhancement and deployment as quantum probes.
