Spin Hall effect in a spin-1 chiral semimetal
Spin Hall effect in a spin-1 chiral semimetal
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DOI：
10.1103/physrevresearch.3.033101
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发表时间：
2021-07-29
影响因子：
4.2
通讯作者：
Mitani, Seiji
中科院分区：
文献类型：
--
作者：
Tang, Ke;Lau, Yong-Chang;Mitani, Seiji
自旋为1的手征半金属是一种量子物质的状态，它拥有非常规的手征费米子，这些费米子超出了常见的狄拉克和外尔费米子。B20型CoSi是容纳这种奇异准粒子的原型材料。到目前为止，自旋1手性半金属的自旋输运性质还没有得到彻底的研究。本文采用磁控溅射法在蓝宝石c面衬底上制备了B20-CoSi薄膜，并结合实验和第一性原理计算研究了薄膜的自旋霍尔效应。利用自旋霍尔磁电阻和谐波霍尔测量方法研究了CoSi/CoFeB/MgO异质结的SHE效应。第一性原理计算得到了与实验一致的费米能级的自旋霍尔电导率（SHC），并揭示了其独特的费米能量依赖性。与狄拉克和外尔费米子介导的霍尔电导率，表现出围绕拓扑节点的峰值状结构，SHC的B20-CoSi是奇数，并在节点处穿过零，两个反对称的本地极值相反的符号位于下面和上面的能量。Co d-Si p轨道之间的杂化和自旋-轨道耦合对于SHC是必不可少的，尽管在费米能级附近的Si p轨道的重量很小（类似于1%）。这项工作扩展了拓扑自旋电子学的视野，并强调了费米能级调谐的重要性，以充分利用自旋1手征费米子的自旋电流产生的拓扑结构。
The spin-1 chiral semimetal is a state of quantum matter hosting unconventional chiral fermions that extend beyond the common Dirac and Weyl fermions. B20-type CoSi is a prototypal material that accommodates such an exotic quasiparticle. To date, the spin-transport properties in the spin-1 chiral semimetals have not been thoroughly explored. In this work, we fabricated B20-CoSi thin films on sapphire c-plane substrates by magnetron sputtering and studied the spin Hall effect (SHE) by combining experiments and first-principles calculations. The SHE of CoSi was investigated using CoSi/CoFeB/MgO heterostructures via spin Hall magnetoresistance and harmonic Hall measurements. First-principles calculations yield an intrinsic spin Hall conductivity (SHC) at the Fermi level that is consistent with the experiments and reveal its unique Fermi-energy dependence. Unlike the Dirac and Weyl fermion-mediated Hall conductivities that exhibit a peaklike structure centering around the topological node, SHC of B20-CoSi is odd and crosses zero at the node with two antisymmetric local extrema of opposite sign situated below and above in energy. Hybridization between Co d-Si p orbitals and spin-orbit coupling are essential for the SHC, despite the small (similar to 1%) weight of the Si p orbital near the Fermi level. This work expands the horizon of topological spintronics and highlights the importance of Fermi-level tuning in order to fully exploit the topology of spin-1 chiral fermions for spin-current generation.