The concept of chirality is of great relevance in nature, from chiral molecules such as sugar to parity transformations in particle physics. In condensed matter physics, recent studies have demonstrated chiral fermions and their relevance in emergent phenomena closely related to topology^1,2,3. The experimental verification of chiral phonons (bosons) remains challenging, however, despite their expected strong impact on fundamental physical properties^4,5,6. Here we show experimental proof of chiral phonons using resonant inelastic X-ray scattering with circularly polarized X-rays. Using the prototypical chiral material quartz, we demonstrate that circularly polarized X-rays, which are intrinsically chiral, couple to chiral phonons at specific positions in reciprocal space, allowing us to determine the chiral dispersion of the lattice modes. Our experimental proof of chiral phonons demonstrates a new degree of freedom in condensed matter that is both of fundamental importance and opens the door to exploration of new emergent phenomena based on chiral bosons.

手性的概念在自然界中具有重要意义，从糖等手性分子到粒子物理学中的宇称变换。在凝聚态物理中，最近的研究证明了手性费米子及其与拓扑密切相关的新兴现象的相关性^1,2,3。然而，手性声子（玻色子）的实验验证仍然具有挑战性，尽管它们预计会对基本物理性质产生强烈影响^4,5,6。在这里，我们使用圆偏振 X 射线共振非弹性 X 射线散射来展示手性声子的实验证明。使用原型手性材料石英，我们证明了本质上手性的圆偏振 X 射线与倒易空间中特定位置的手性声子耦合，使我们能够确定晶格模式的手性色散。我们对手性声子的实验证明证明了凝聚态物质的新自由度，这不仅具有根本重要性，而且为探索基于手性玻色子的新出现现象打开了大门。