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arXiv 2204.07910cond-mat.mtrl-scicond-mat.mes-hall
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单轴应力下二维铁磁半导体VSe2中可能的结构与键重构

Possible structural and bond reconstruction in 2D ferromagnetic semiconductor VSe2 under uniaxial stress

Bo-Wen Yu, Bang-Gui Liu

AI总结:

该研究通过第一性原理计算发现,单轴应力或应变可使二维铁磁半导体VSe2从H相转变为能量更低的H'相,增强铁磁性并改变电子结构,实现结构与键重构。

摘要:

二维半导体过渡金属二硫化物已被用于制造高性能电子、自旋电子和光电器件。最近,在二维VSe$_2$纳米片(机械剥离到带有氧化物层的硅衬底上)中发现了室温铁磁性和半导体性质,这归因于二维极限下VSe$_2$的稳定2H相。在此,我们的第一性原理研究表明,当这些二维H相材料处于单轴应力或单轴应变下时,可以从H VSe2单层及其他一些类似材料形成亚稳态半导体H'相。对于单轴应力(单轴应变)方案,在转变点处H'相的总能量将低于H相。计算的声子谱表明VSe$_2$、VS$_2$和CrS$_2$的H'结构具有动力学稳定性,并计算了H和H' VSe$_2$相之间的相切换路径。对于VSe$_2$,H'相具有更强的铁磁性,其居里温度可以通过施加单轴应力或应变显著提高。对于H和H'两相,自旋分辨电子结构、能带边缘和有效载流子质量都可以通过施加的单轴应力或应变显著改变,导致应变H'相在带边附近出现巨大的有效质量。分析表明,H'相与H相之间的最大键长差对于Se3-Se3'键可达-19%,且Se3-Se3'键存在明显的共价性,这切换了附近V原子的价态,导致铁磁性增强。因此,通过施加单轴应力可以在二维铁磁H VSe$_2$及其他一些类似材料中实现结构和键重构。这些有助于在潜在应用中寻求此类二维材料中更多的见解和现象。

英文摘要:

2D semiconducting transition metal dichalcogenides have been used to make high-performance electronic, spintronic, and optoelectronic devices. Recently, room-temperature ferromagnetism and semiconducting property were found in 2D VSe$_2$ nanoflakes (mechanically exfoliated onto silicon substrates capped with a oxide layer) and are attributed to the stable 2H-phase of VSe$_2$ in the 2D limit. Here, our first-principles investigation show that a metastable semiconducting H' phase can be formed from the H VSe2 monolayer and some other similar when these 2D H-phase materials are under uniaxial stress or uniaxial strain. For the uniaxial stress (uniaxial strain) scheme, the H' phase will become lower in total energy than the H phase at the transition point. The calculated phonon spectra indicate the dynamical stability of the H' structures of VSe$_2$, VS$_2$, and CrS$_2$, and the path of phase switching between the H and H' VSe$_2$ phases is calculated. For VSe$_2$, the H' phase has stronger ferromagnetism and its Currier temperature can be substantially enhanced by applying uniaxial stress or strain. Spin-resolved electronic structures, energy band edges, and effective carrier masses for both of the H and H' phases can be substantially changed by the applied uniaxial stress or strain, leading to huge effective masses near the band edge of the strained H' phase. Analysis indicated that the largest bond length difference between the H' and H phases can reach -19\% for the Se3-Se3' bond, and there is noticeable covalence for the Se3-Se3' bond, which switches the valence of the nearby V atoms, leading to the enhanced ferromagnetism. Therefore, structural and bond reconstruction can be realized by applying uniaxial stress in 2D ferromagnetic H VSe$_2$ and some other similar. These can be useful to seeking more insights and phenomena in such 2D materials for potential applications.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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