Chirality refers to a structure that lacks mirror symmetry. It can be observed in a wide range of platforms, from subatomic particles and molecules to living organisms. However, the underlying mechanisms that give rise to chirality in condensed matter systems have been a subject of considerable interest. Here we elucidate the mechanism of chiral charge density wave formation in the transition-metal dichalcogenide 1T-TiSe₂. Based on symmetry analysis, we demonstrate that charge density modulations and ionic displacements follow distinct irreducible representations of the space group, despite exhibiting similar wave vectors and a strong coupling. This charge-lattice symmetry frustration induces lattice distortions that further break all symmetries that are not common to both sectors. This ultimately gives rise to chirality. Our theory is verified using Raman spectroscopy and inelastic X-ray scattering.

手性是指缺乏镜像对称性的结构。它可以在各种平台上进行观测，从亚原子粒子和分子到生物体。然而，在凝聚态系统中产生手性的潜在机制一直是一个相当有趣的主题。在这里，我们阐明了过渡金属二硫化物 1T-TiSe₂ 中手性电荷密度波形成的机制。基于对称性分析，我们证明了电荷密度调制和离子位移遵循空间群的不同不可约表示，尽管表现出相似的波矢和强耦合。这种电荷-晶格对称性挫折会引起晶格畸变，从而进一步打破两个扇区不常见的所有对称性。这最终产生了手性。我们的理论使用拉曼光谱和非弹性 X 射线散射进行了验证。