Kanazawa N, Kitaori A, White J S, Ukleev V, Rønnow H M, Tsukazaki A, Ichikawa M, Kawasaki M, Tokura Y
Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.
Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland.
Phys Rev Lett. 2020 Sep 25;125(13):137202. doi: 10.1103/PhysRevLett.125.137202.
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.
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涌现磁单极子，即与传导电子强烈耦合的规范场的量子化源和汇，并导致诸如巨大霍尔效应等非常规输运响应。通过磁输运和小角中子散射（SANS）的联合测量，我们观察到手性磁体MnGe中自旋刺猬晶体转变时霍尔效应的显著变化。在低温下，明确的SANS峰和负霍尔信号均与静态刺猬晶格的预期相符。相比之下，当刺猬晶格在较高温度下波动时，正霍尔信号占主导，并且在刺猬晶格分解时观察到漫射SANS信号。我们的方法提供了一种简单的方式，既能区分又能解开静态和动态涌现磁单极子对传导电子增强霍尔运动的作用。
