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Thermal Hall and Nernst responses in ultrathin magnetic films of pyrochlore lattice
Journal of Physics: Condensed Matter ( IF 2.7 ) Pub Date : 2021-05-24 , DOI: 10.1088/1361-648x/abf976
Bahman Sheikhi , Mehdi Kargarian , Abdollah Langari

The ultrathin films of pyrochlore lattice along [111] direction provide a fertile ground for exploring topological states in oxide materials, where the electron correlations are strong and magnetically ordered states are favored. As a result of strong interactions, most of states are magnetic insulators with strong Dzyaloshinskii–Moriya and anisotropic spin interactions. We considered three types of heterostructures, a bilayer of triangular-kagome (TK), and two trilayers of triangular-kagome-triangular (TKT) and kagome-triangular-kagome (KTK) thin films. The ground states are magnetically ordered with the low-energy excitations, the magnons, characterized by nontrivial topology. While for TK model the lowest magnon band is trivial, the lowest bands in TKT and KTK model are topological. These features have direct consequences on the thermal Hall conductivity, where we observed that the latter quantity onsets at lower temperature in multilayer models, suggesting that the thermal Hall response can be controlled by engineering lattice-driven magnetic band structure. We also introduce the thermal sublattice Nernst effect in these layers and found the corresponding response is as large as the thermal Hall response.



中文翻译:

烧绿石晶格超薄磁膜中的热霍尔和能斯特响应

烧绿石晶格沿 [111] 方向的超薄膜为探索氧化物材料中的拓扑态提供了肥沃的土壤,其中电子相关性强且磁有序态是有利的。由于强相互作用,大多数状态是具有强 Dzyaloshinskii-Moriya 和各向异性自旋相互作用的磁绝缘体。我们考虑了三种类型的异质结构,三角形-kagome (TK) 的双层和三角形-kagome-triangular (TKT) 和 kagome-triangular-kagome (KTK) 薄膜的两个三层。基态是用低能量激发磁子排列的,磁振子以非平凡的拓扑结构为特征。而对于 TK 模型,最低的磁子能带是微不足道的,而 TKT 和 KTK 模型中的最低能带是拓扑的。这些特征对热霍尔传导率有直接影响,我们观察到后者在多层模型中的温度较低时开始,这表明热霍尔响应可以通过工程晶格驱动的磁带结构来控制。我们还在这些层中引入了热亚晶格 Nernst 效应,发现相应的响应与热霍尔响应一样大。

更新日期:2021-05-24
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