The electronic band structure of crystals is generally influenced by the periodic arrangement of their constituent atoms. Specifically, the emerging two-dimensional (2D) layered structures have shown different band structures with respect to their stacking configurations. Here, based on first-principles density-functional theory calculations, we demonstrate that the band structure of the recently synthesized 2D Ca$_2$N electride changes little for the stacking sequence as well as the lateral interlayer shift. This intriguing invariance of band structure with respect to geometrical variations can be attributed to a complete screening of [Ca$_2$N]$^{+}$ cationic layers by anionic excess electrons delocalized between the cationic layers. The resulting weak interactions between 2D dressed cationic layers give rise to not only a shallow potential barrier for bilayer sliding but also an electron-doping facilitated shear exfoliation. Our findings open a route for exploration of the peculiar geometry-insensitive electronic properties in 2D electride materials, which will be useful for future thermally stable electronic applications.
Enrichment of rhombohedral stacking by mechanical exfoliation of graphite
Hungarian Research Network, Centre for Energy Research（匈牙利研究网络能源研究中心）；MTA - HUN-REN EK Lendület “Momentum” Topology in Nanomaterials Research Group（MTA-HUN-REN EK Lendulet“动量”纳米材料拓扑研究组）；Óbuda University（奥比乌斯大学）；Budapest University of Technology and Economics（布达佩斯技术与经济大学）；ELTE Eötvös Loránd University（罗兰大学）
Non-van der Waals honeycomb antiferromagnet SrRu$_2$O$_6$ down to a few layers
目前实验实现的二维磁性材料家族由3个$d$过渡金属组成，具有非常弱的自旋-轨道耦合。相比之下，我们报告了一个新的平台，在化学键合和分层4 $d$氧化物，具有较强的电子相关性和竞争的自旋轨道耦合。我们合成超薄片的SrRu $_2$ O $_6$使用可扩展的液体剥离。这些剥离片的特征在于互补的实验和理论技术。纳米片的厚度在三到五个单层之间变化，并且在第一性原理计算内，我们表明反铁磁性在这些超薄层中存活。实验数据表明，剥离发生从垂直于$c$轴的平面作为中介的六方Sr晶格分离的二维磁性蜂窝状Ru层。高分辨率透射电子显微镜图像表明，Ru层之间的平均原子间距略有减少，这与目前的计算结果一致。还观察到纳米片的旋转堆叠的签名。这种新的二维平台提供了巨大的可能性，以探索由于磁性，强相关性和自旋轨道耦合之间的相互作用而出现的新特性。此外，这些效果可以进一步作为层厚度的函数来调节。
