The asymmetric distribution of chiral objects with opposite chirality is of great fundamental interest ranging from molecular biology to particle physics. In quantum materials, chiral states can build on inversion-symmetry-breaking lattice structures or emerge from spontaneous magnetic ordering induced by competing interactions. Although the handedness of a chiral state can be changed through external fields, a spontaneous chirality flipping has yet to be discovered. We present experimental evidence of chirality flipping via changing temperature in a topological magnet ${\mathrm{EuAl}}_4$, which features orthogonal spin density waves (SDW) and charge density waves (CDW). Using circular dichroism of Bragg peaks in the resonant magnetic x-ray scattering, we find that the chirality of the helical SDW flips through a first-order phase transition with modified SDW wavelength. Intriguingly, we observe that the CDW couples strongly with the SDW and displays a rare commensurate-to-incommensurate transition at the chirality flipping temperature. Combining with first-principles calculations and angle-resolved photoemission spectroscopy, our results support a Fermi surface origin of the helical SDW with intertwined spin, charge, and lattice degrees of freedom in ${\mathrm{EuAl}}_4$. Our results reveal an unprecedented spontaneous chirality flipping and lay the groundwork for a new functional manipulation of chirality through momentum-dependent spin-charge-lattice interactions.

中文翻译：

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正交自旋电荷有序拓扑磁体中的自发手性翻转

具有相反手性的手性物体的不对称分布在从分子生物学到粒子物理学的各个领域都具有重要的基础意义。在量子材料中，手性态可以建立在反演对称性破缺的晶格结构上，或者从竞争相互作用引起的自发磁有序中出现。尽管手性态的手性可以通过外部场改变，但自发的手性翻转尚未被发现。我们提出了拓扑磁体中通过改变温度来实现手性翻转的实验证据${\mathrm{欧盟铝}}_4$，其特征是正交自旋密度波（SDW）和电荷密度波（CDW）。利用共振磁 X 射线散射中布拉格峰的圆二色性，我们发现螺旋 SDW 的手性会随着修改的 SDW 波长翻转一级相变。有趣的是，我们观察到 CDW 与 SDW 强烈耦合，并在手性翻转温度下表现出罕见的相称到不相称的转变。结合第一性原理计算和角分辨光电子能谱，我们的结果支持螺旋 SDW 的费米表面起源，其自旋、电荷和晶格自由度相互交织。${\mathrm{欧盟铝}}_4$。我们的结果揭示了前所未有的自发手性翻转，并为通过动量依赖的自旋电荷晶格相互作用对手性进行新的功能操纵奠定了基础。