Chen Y, Gaudet J, Dasgupta S, Marcus G G, Lin J, Chen T, Tomita T, Ikhlas M, Zhao Y, Chen W C, Stone M B, Tchernyshyov O, Nakatsuji S, Broholm C
Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Phys Rev B. 2020 Aug;102(5). doi: 10.1103/PhysRevB.102.054403.
We report the magnetic structure and spin excitations of , a breathing kagome antiferromagnet with transport anomalies attributed to Weyl nodes. Using polarized neutron diffraction, we show the magnetic order is a coplanar state belonging to a irreducible representation, which can be described as a perfect 120° antichiral structure with a moment of , superimposed with weak collinear ferromagnetism. Inelastic neutron scattering shows three collective excitations at , , and . A field theory of spin waves in triangular antiferromagnets with a 120° spin structure was used to classify these modes. The in-plane mode is gapless, is the gap to a doublet of out-of-plane spin excitations ( , ), and , result from hybridization of optical phonons with magnetic excitations. While a phenomenological spin Hamiltonian including exchange interactions, Dzyaloshinskii-Moriya interactions, and single-ion crystal field terms can describe aspects of the Mn-based magnetism, spin-wave damping [ ] and the extended range of magnetic interactions indicate itinerant magnetism consistent with the transport anomalies.
我们报道了一种具有归因于外尔节点的输运异常的呼吸式 Kagome 反铁磁体的磁结构和自旋激发。利用极化中子衍射，我们表明磁序是一种属于不可约表示的共面状态，可描述为具有磁矩的完美 120°反螺旋结构，叠加有弱共线铁磁性。非弹性中子散射显示在 、 和 处有三种集体自旋激发。利用具有 120°自旋结构的三角反铁磁体中自旋波的场论对这些模式进行了分类。面内模式 是无隙的， 是面外自旋激发二重态（ ， ）的能隙，而 、 是光学声子与磁激发杂化的结果。虽然包含交换相互作用、Dzyaloshinskii-Moriya 相互作用和单离子晶体场项的唯象自旋哈密顿量可以描述基于锰的磁性的一些方面，但自旋波阻尼[ ]和扩展的磁相互作用范围表明与输运异常一致的巡游磁性。
