In the three-dimensional (3D) Heisenberg model, topological point defects known as spin hedgehogs behave as emergent magnetic monopoles, i.e., quantized sources and sinks of gauge fields that couple strongly to conduction electrons, and cause unconventional transport responses such as the gigantic Hall effect. We observe a dramatic change in the Hall effect upon the transformation of a spin hedgehog crystal in a chiral magnet MnGe through combined measurements of magnetotransport and small-angle neutron scattering (SANS). At low temperatures, well-defined SANS peaks and a negative Hall signal are each consistent with expectations for a static hedgehog lattice. In contrast, a positive Hall signal takes over when the hedgehog lattice fluctuates at higher temperatures, with a diffuse SANS signal observed upon decomposition of the hedgehog lattice. Our approach provides a simple way to both distinguish and disentangle the roles of static and dynamic emergent monopoles on the augmented Hall motion of conduction electrons.

中文翻译：

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直接观察手性磁体中出现的电磁单极的静力学和动力学

在三维（3D）海森堡模型中，被称为自旋刺猬的拓扑点缺陷表现为新兴的磁单极子，即，量子场的量子化源和阱，它们与传导电子强烈耦合，并引起非常规的传输响应，例如巨大的霍尔影响。通过结合磁传输和小角度中子散射（SANS）的测量，我们观察到手性磁体MnGe中自旋刺猬晶体转变的霍尔效应发生了巨大变化。在低温下，清晰定义的SANS峰值和负霍尔信号均与静态刺猬晶格的预期一致。相反，当刺猬晶格在较高温度下波动时，正的霍尔信号将接管，而在刺猬晶格分解时会观察到漫射SANS信号。