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arXiv 2202.09431cond-mat.mtrl-sci
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反铁磁双层膜CrI3中Rashba诱导的自旋织构和自旋层锁定效应

Rashba-induced spin texture and spin-layer-locking effects in the antiferromagnetic CrI3 bilayer

Sukanya Ghosh, Natasa Stojic, Nadia Binggeli

摘要:

反铁磁(AFM)CrI $_3$双层是范德华二维半导体的一个特别有趣的代表,目前正在研究它们的磁性和自旋电子学的潜力。利用从头算密度泛函理论计算,研究了原子力显微镜CrI $_3$双层膜(双简并)最高价带带态在动量空间中的自旋织构,Cr自旋磁矩垂直于膜层.我们发现存在的,在布里渊区的主要中心部分,在两层上的相反的符号的Rashba面内自旋纹理,从内在的本地电场作用于每一层。为了研究波函数的层分离,我们施加了一个小的电场,根据它们的层占有率分裂简并态。我们发现最高价带的波函数是层偏聚的,只属于具有相反面内自旋织构的两层中的一层,而且这种层偏聚几乎发生在整个布里渊区。面内倾斜自旋的相应层锁定与最高AFM带与其余价带的能量分离有关。我们解释了能带相互作用如何破坏$K$、$K'$和$Γ$点的层锁定。此外,我们比较了在我们的原子力显微镜双层系统中的平面倾斜自旋的层锁定与隐藏的自旋极化在中心对称的双折射材料,指出在隔离机制和它们的后果层锁定的差异。我们注意到,类似的Rashba效应与层锁定的面内倾斜的自旋可以发生在其他范德华力原子力显微镜双层膜与强自旋轨道耦合和一个孤立的能带。

英文摘要:

The antiferromagnetic (AFM) CrI$_3$ bilayer is a particularly interesting representative of van der Waals 2D semiconductors, which are currently being studied for their magnetism and for their potential in spintronics. Using ab initio density-functional theory calculations, we investigate the spin texture in momentum space of the states of the (doubly degenerate) highest valence band of the AFM CrI$_3$ bilayer with Cr-spin moments perpendicular to the layers. We find the existence, in the main central part of the Brillouin zone, of a Rashba in-plane spin texture of opposite signs on the two layers, resulting from the intrinsic local electric fields acting on each layer. To study the layer segregation of the wavefunctions, we apply a small electric field that splits the degenerate states according to their layer occupancy. We find that the wavefunctions of the highest valence band are layer-segregated, belonging to only one of the two layers with opposite in-plane spin textures, and the segregation occurs over nearly the whole Brillouin zone. The corresponding layer locking of the in-plane-canted spin is related to the separation in energy of the highest AFM band from the rest of the valence bands. We explain how the band interactions destroy the layer locking at the $K$, $K'$, and $Γ$ points. Furthermore, we compare the layer locking of the in-plane-canted spin in our AFM bilayer system with the hidden spin polarization in centrosymmetric nonmagnetic materials, pointing out the differences in segregation mechanisms and their consequences for the layer locking. We note that a similar Rashba effect with layer locking of in-plane-canted spin could occur in other van der Waals AFM bilayers with strong spin-orbit coupling and an isolated energy band.

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