The robust spin and momentum valley locking of electrons in two-dimensional semiconductors makes the valley degree of freedom of great utility for functional optoelectronic devices. Owing to the difference in optical selection rules for the different valleys, these valley electrons can be addressed optically. The electrons and excitons in these materials exhibit the valley Hall effect, where the carriers from specific valleys are directed to different directions under electrical or thermal bias. Here we report the optical analog of valley Hall effect, where the light emission from the valley-polarized excitons in a monolayer ${{\rm WS}_2}$ propagates in different directions owing to the preferential coupling of excitonic emission to the high momentum states of the hyperbolic metamaterial. The experimentally observed effects are corroborated with theoretical modeling of excitonic emission in the near field of hyperbolic media. The demonstration of the optical valley Hall effect using a bulk artificial photonic media without the need for nanostructuring opens the possibility of realizing valley-based excitonic circuits operating at room temperature.

中文翻译：

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双曲超材料中二维激子谷霍尔效应的光学模拟

电子在二维半导体中的稳健的自旋和动量谷锁定使得谷自由度对于功能性光电器件具有很大的实用性。由于针对不同波谷的光学选择规则的差异，可以对这些波谷电子进行光学寻址。这些材料中的电子和激子表现出谷霍尔效应，其中特定谷的载流子在电或热偏压下被导向不同的方向。在这里，我们报告了谷霍尔效应的光学模拟，其中单层$ {{\ rm WS} _2} $中谷极化激子的光发射由于激子发射与双曲线超材料的高动量态之间的优先耦合，因此沿不同方向传播。实验观察到的效果与双曲线介质近场中激子发射的理论模型得到了证实。利用大量人工光子介质无需纳米结构就可以演示光学谷霍尔效应，这为实现基于谷的激子电路在室温下运行提供了可能性。