Spin–orbit coupling is a fundamental mechanism that connects the spin of a charge carrier with its momentum. In the optical domain, an analogous synthetic spin–orbit coupling is accessible by engineering optical anisotropies in photonic materials. Both yield the possibility of creating devices that directly harness spin and polarization as information carriers. Atomically thin transition metal dichalcogenides promise intrinsic spin-valley Hall features for free carriers, excitons and photons. Here we demonstrate spin- and valley-selective propagation of exciton-polaritons in a monolayer of MoSe₂ that is strongly coupled to a microcavity photon mode. In a wire-like device we trace the flow and helicity of exciton-polaritons expanding along its channel. By exciting a coherent superposition of K and K′ tagged polaritons, we observe valley-selective expansion of the polariton cloud without either an external magnetic field or coherent Rayleigh scattering. The observed optical valley Hall effect occurs on a macroscopic scale, offering the potential for applications in spin-valley-locked photonic devices.

自旋-轨道耦合是一种将电荷载流子的自旋与其动量联系起来的基本机制。在光学领域，通过光子材料中的工程光学各向异性可以访问类似的合成自旋-轨道耦合。两者都产生了创建直接利用自旋和极化作为信息载体的设备的可能性。原子上较薄的过渡金属二卤化物有望为自由载流子，激子和光子提供固有的自旋谷霍尔特性。在这里，我们展示了MoSe ₂单层中激子极化子的自旋和谷选择性传播。它与微腔光子模式紧密耦合。在线状设备中，我们跟踪激子-极化子沿其通道扩展的流量和螺旋度。通过激发K和K'标记的极化子的相干叠加，我们观察到极化子云的谷选择性扩展，而没有外部磁场或相干瑞利散射。观察到的光学谷霍尔效应发生在宏观尺度上，为自旋谷锁定光子器件的应用提供了潜力。