Two-dimensional (2D) materials and heterostructures with strong excitonic effect and spin/valley properties have emerged as an exciting platform for optoelectronic and spin/valleytronic applications. There, precise control of the exciton transformation process (including intralayer to interlayer exciton transition and recombination) and valley polarization process via structural tuning is crucial but remains largely unexplored. Here, using hexagonal boron nitride (BN) as an intermediate layer, we show the fine-tuning of exciton and valley dynamics in 2D heterostructures with atomic precision. Both interfacial electron and hole transfer rates decrease exponentially with increasing BN thickness, which can be well-described with quantum tunneling model. The increased spatial separation with BN intercalation weakens the electron-hole Coulomb interaction and significantly prolongs the interlayer exciton population and valley polarization lifetimes in van der Waals (vdW) heterostructures. For example, WSe2/WS2 heterostructures with monolayer BN intercalation exhibit a hole valley polarization lifetime of ∼60 ps at room temperature, which is approximately threefold and 3 orders of magnitude longer than that in WSe2/WS2 heterobilayer without BN and WSe2 monolayer, respectively. Considering a large family of layered materials, this study suggests a general approach to tailor and optimize exciton and valley properties in vdW heterostructures with atomic precision.

中文翻译：

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用原子精确的层间邻近度控制二维异质结构中的激子和谷动力学。

具有强激子效应和自旋/谷特性的二维（2D）材料和异质结构已成为光电和自旋/谷电子应用的令人兴奋的平台。在那里，通过结构调整来精确控制激子转变过程（包括层内到层间的激子过渡和复合）和谷极极化过程非常关键，但在很大程度上尚待探索。在这里，使用六方氮化硼（BN）作为中间层，我们以原子精度显示了二维异质结构中激子和谷值动力学的微调。随着BN厚度的增加，界面电子和空穴传输速率均呈指数下降，这可以用量子隧穿模型很好地描述。BN插入增加的空间间隔会削弱电子-空穴库仑相互作用，并显着延长范德华（vdW）异质结构中的层间激子数量和谷极化寿命。例如，具有单层BN插层的WSe2 / WS2异质结构在室温下的孔谷极化寿命为〜60 ps，分别比不具有BN和WSe2单层的WSe2 / WS2异质双层的空穴谷极化寿命大约长三倍和3个数量级。考虑到大量的层状材料，这项研究提出了一种以原子精度调整和优化vdW异质结构中激子和谷性质的通用方法。例如，具有单层BN插层的WSe2 / WS2异质结构在室温下的孔谷极化寿命为〜60 ps，分别比不具有BN和WSe2单层的WSe2 / WS2异质双层的空穴谷极化寿命大约长三倍和3个数量级。考虑到大量的层状材料，这项研究提出了一种以原子精度调整和优化vdW异质结构中激子和波谷性质的通用方法。例如，具有单层BN插层的WSe2 / WS2异质结构在室温下的孔谷极化寿命为〜60 ps，分别比不具有BN和WSe2单层的WSe2 / WS2异质双层的空穴谷极化寿命大约长三倍和3个数量级。考虑到大量的层状材料，这项研究提出了一种以原子精度调整和优化vdW异质结构中激子和波谷性质的通用方法。