The synthetic tunability, flexibility, and rich spin physics of semiconductor quantum dots make them promising candidates for quantum information science applications. However, the rapid spin relaxation observed in colloidal quantum dots limits their functionality. In the current work, we demonstrate a method to harness photoexcited spin states in QDs to produce long-lived spin polarization on an appended organic ligand molecule. We present a system composed of CdSe/CdS core/shell QDs, covalently linked to naphthalenediimide (NDI) electron accepting molecules. The electron transfer dynamics from photoexcited QDs to the appended NDI ligands is explored as a function of both shell thickness and number of NDIs per quantum dot. Transient EPR spectroscopy shows that the photoexcited QDs strongly spin polarize the NDI radical anion, which is interpreted in the context of both the radical pair and triplet mechanisms of spin polarization. This work serves an initial step towards using photoexcited QDs to strongly spin polarize organic radicals having long spin relaxation times to serve as spin qubits in quantum information science applications.

中文翻译：

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使用光激发核/壳量子点自旋极化附加自由基量子位

半导体量子点的合成可调性、灵活性和丰富的自旋物理使其成为量子信息科学应用的有希望的候选者。然而，在胶体量子点中观察到的快速自旋弛豫限制了它们的功能。在目前的工作中，我们展示了一种利用量子点中的光激发自旋态在附加的有机配体分子上产生长寿命自旋极化的方法。我们提出了一个由 CdSe/CdS 核/壳量子点组成的系统，共价连接到萘二亚胺 (NDI) 电子接受分子。从光激发量子点到附加 NDI 配体的电子转移动力学被探索为壳厚度和每个量子点 NDI 数量的函数。瞬态 EPR 光谱显示光激发的 QD 强烈自旋极化 NDI 自由基阴离子，这在自旋极化的自由基对和三重态机制的背景下进行解释。这项工作是朝着使用光激发量子点强自旋极化具有长自旋弛豫时间的有机基团作为量子信息科学应用中的自旋量子位的第一步。