[论文解读] Optical read and write of spin states in organic diradicals

Rituparno Chowdhury, Petri Murto+18 more|arXiv (Cornell University)|Jun 5, 2024

Diamond and Carbon-based Materials Research被引用 5

一句话总结

该论文在含有两个 trityl 基团的二自由基分子中展示了自旋-光学可寻址性，显示单态/三重态的光致发光、极小的基态自旋交换，以及高光致发光量子产率，从而实现自旋-光子接口。

ABSTRACT

Optical control and read-out of the ground state spin structure has been demonstrated for defect states in crystalline semiconductors, including the diamond NV- center, and these are promising systems for quantum technologies. Molecular organic semiconductors offer synthetic control of spin placement, in contrast to current limitations in these crystalline systems. Here we report the discovery of spin-optical addressability in a diradical molecule that comprises two trityl radical groups coupled via a fluorene bridge. We demonstrate the three important properties that enable operation as a spin-photon interface: (i) triplet and singlet spin states show photoluminescence peaked at 640 and 700 nm respectively; this allows easy optical measurement of ground state spin. (ii) the ground state spin exchange is small (~60 μeV) that allows preparation of ground state spin population. This can be achieved by spin-selective excited state intersystem crossing, and we report up to 8% microwave-driven contrast in photoluminescence. (iii) both singlet and triplet manifolds have near-unity photoluminescence quantum yield, which is in contrast to the near-zero quantum yields in prior reports of molecular diradicals. Our results establish these tuneable open-shell organic molecules as a platform to engineer tailor-made spin-optical interfaces.

研究动机与目标

• 展示有机二自由基体系中基态自旋的光学控制与读出。
• 展示能够实现基态自旋制备的自旋选择性路径。
• 建立在可调有机分子中实现自旋-光子接口的特性。

提出的方法

• 研究一个通过芴桥连接的两个 trityl 自由基基团的二自由基分子。
• 表征单态和三重态下的光致发光，分别在 700 nm 与 640 nm。
• 量化基态自旋交换并演示自旋选择性激发态内系统跳跃。
• 测量单态和三重态下的光致发光量子产率（photoluminescence quantum yields）。

实验结果

研究问题

• RQ1 有机二自由基是否能够表现出通过光学方式可寻址并能通过光致发光检测的自旋态？
• RQ2 在该分子平台中实现自旋-光子接口的关键特性是什么？
• RQ3 基态自旋交换是否足够小以实现自旋群体的制备？
• RQ4 单态和三重态的光致发光效率（量子产率）是多少？

主要发现

• 三重态和单态在 640 nm 与 700 nm 处显示光致发光峰，能够对基态自旋进行光学测量。
• 基态自旋交换很小（约 60 μeV），使得通过自旋选择性路径实现基态自旋群的制备成为可能。
• 单态和三重态两者的光致发光量子产率接近单位值。
• 在光致发光中实现了高达 8% 的微波驱动对比度。
• 这些结果将二自由基系统定位为有机半导体中的可调自旋-光子接口。