Unconventional Charge-Spin Conversion in Weyl-Semimetal WTe2.,Advanced Materials

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Unconventional Charge-Spin Conversion in Weyl-Semimetal WTe2.
Advanced Materials ( IF 27.4 ) Pub Date : 2020-08-09 , DOI: 10.1002/adma.202000818
Bing Zhao _{1,

2} , Bogdan Karpiak ₂ , Dmitrii Khokhriakov ₂ , Annika Johansson _{3,

4} , Anamul Md Hoque ₂ , Xiaoguang Xu ₁ , Yong Jiang ₁ , Ingrid Mertig _{3,

4} , Saroj P Dash _{2,

5}

Affiliation

An outstanding feature of topological quantum materials is their novel spin topology in the electronic band structures with an expected large charge‐to‐spin conversion efficiency. Here, a charge‐current‐induced spin polarization in the type‐II Weyl semimetal candidate WTe₂ and efficient spin injection and detection in a graphene channel up to room temperature are reported. Contrary to the conventional spin Hall and Rashba–Edelstein effects, the measurements indicate an unconventional charge‐to‐spin conversion in WTe₂, which is primarily forbidden by the crystal symmetry of the system. Such a large spin polarization can be possible in WTe₂ due to a reduced crystal symmetry combined with its large spin Berry curvature, spin–orbit interaction with a novel spin‐texture of the Fermi states. A robust and practical method is demonstrated for electrical creation and detection of such a spin polarization using both charge‐to‐spin conversion and its inverse phenomenon and utilized it for efficient spin injection and detection in the graphene channel up to room temperature. These findings open opportunities for utilizing topological Weyl materials as nonmagnetic spin sources in all‐electrical van der Waals spintronic circuits and for low‐power and high‐performance nonvolatile spintronic technologies.

中文翻译：

Weyl-Semimetal WTe2中的非常规电荷自旋转换。

拓扑量子材料的一个突出特点是它们在电子能带结构中具有新颖的自旋拓扑结构，并具有很高的电荷自旋转换效率。此处报道了II型Weyl半金属候选物WTe _2中的电荷电流诱导的自旋极化，以及在高达室温的石墨烯通道中的有效自旋注入和检测。与传统的自旋霍尔效应和Rashba-Edelstein效应相反，这些测量表明WTe _2中存在非常规的电荷转自旋转换，这主要是由于系统的晶体对称性所禁止的。在WTe _2中如此大的自旋极化是可能的由于降低的晶体对称性及其大的自旋贝里曲率，自旋轨道相互作用与费米态的新型自旋结构。演示了一种可靠且实用的方法，可利用电荷到自旋转换及其逆现象同时创建和检测这种自旋极化，并利用该方法有效地自旋注入并在高达室温的石墨烯通道中进行检测。这些发现为将拓扑Weyl材料用作全电范德华自旋电子电路中的非磁性自旋源以及低功率和高性能非易失性自旋电子技术提供了机会。

更新日期：2020-09-21

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