二维 NbSe2 和 NbS2 中的结构、电子相变和热自旋输运特性：第一性原理研究,Physical Chemistry Chemical Physics

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二维 NbSe2 和 NbS2 中的结构、电子相变和热自旋输运特性：第一性原理研究
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2022-10-13 , DOI: 10.1039/d2cp03417d
Yuqi Liu ₁ , Yulin Feng ₂ , Lei Hu ₁ , Xuming Wu ₃ , Shuang Qiao ₄ , Guoying Gao ₁

Affiliation

如何有效地调谐二维电子和磁性是开发新型自旋电子材料和器件的关键。_{尽管已经在 2H NbSe 2}和 NbS ₂单层中研究了应变诱导的金属-半金属电子相变 (EPT) ，但尚未探索 1T 相、库仑相互作用和传输特性。在这里，我们结合非平衡格林函数使用第一性原理计算，对 NbSe ₂和 NbS _{2的应变调谐结构、电子、磁和热自旋输运特性进行了全面的比较研究}具有和不具有库仑相互作用的单分子层。发现库仑相互作用使应变诱导的 2H 到 1T 结构相变更容易。与2H相类似，对于没有库仑相互作用的1T相也存在应变诱导的金属-半金属EPT，库仑相互作用使ETP更容易。值得注意的是，具有库仑相互作用的2H-NbSe ₂单层是一种双极自旋无带隙半导体（SGS），新型狄拉克半金属和通常的SGS可以通过拉伸应变获得。此外，我们预测 2H-NbSe _{2的双极 SGS 具有出色的自旋塞贝克效应和热自旋二极管效应}具有库仑相互作用的单分子层，并期望在应变驱动的半金属中产生自旋过滤效应和高磁阻。我们还通过比较理论和可用的实验电子态来讨论库仑相互作用的强度，表明库仑相互作用的不可或缺性。这些结果表明，二维 NbSe ₂和 NbS ₂是相变自旋电子材料和器件的有前途的候选者，并将促进对此类二维系统的广泛研究。

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Structural, electronic phase transitions and thermal spin transport properties in 2D NbSe2 and NbS2: a first-principles study

How to effectively tune 2D electronic and magnetic properties is key to developing novel spintronic materials and devices. Although the strain induced metal-to-half-metal electronic phase transition (EPT) has been studied in 2H NbSe₂ and NbS₂ monolayers, the 1T phase, the Coulomb interaction and the transport properties have not been explored. Here, using first-principles calculations in junction with nonequilibrium Green's function, we present a comprehensive and comparative study on the strain tuned structural, electronic, magnetic and thermal spin transport properties for NbSe₂ and NbS₂ monolayers with and without Coulomb interaction. It is found that the Coulomb interaction makes the strain induced 2H-to-1T structural phase transition easier. Similar to the 2H phase, there is also a strain induced metal-to-half-metal EPT for the 1T phase without Coulomb interaction, and the Coulomb interaction makes the ETP easier. Remarkably, the 2H-NbSe₂ monolayer with Coulomb interaction is a bipolar spin gapless semiconductor (SGS), and novel Dirac half-metal and usually SGS can be obtained by the tensile strain. In addition, we predict the excellent spin Seebeck effect and thermal spin diode effect in the bipolar SGS of the 2H-NbSe₂ monolayer with Coulomb interaction, and expect the spin filtering effect and high magnetoresistance in the half-metals driven by the strain. We also discuss the strength of Coulomb interaction by comparing the theoretical and available experimental electronic states, indicating the indispensability of Coulomb interactions. These results suggest that 2D NbSe₂ and NbS₂ are promising candidates for phase-change spintronic materials and devices, and will stimulate extensive studies on this class of 2D systems.

更新日期：2022-10-13

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