具有高迁移率和可调磁性的双碱金属单硫族化合物半导体
Dialkali-Metal Monochalcogenide Semiconductors with High Mobility and Tunable Magnetism
摘要：
原型二维（2D）材料的发现为基础突破和器件应用提供了巨大的机会，正如过去十年中石墨烯，原子薄过渡金属硫属化物和少层黑磷的研究蓬勃发展所证明的那样。在这里，我们报告了一个新的，大家庭的半导体二碱金属单硫族化物（DMMCs）与固有的A $_{2}$ X单层结构，其中两个碱金属亚单层形成六方密堆积和三明治的三角形硫族元素原子平面。这种独特的晶格结构导致了非凡的物理性质，例如良好的动态和热稳定性、可见的近红外线能隙、高电子迁移率（例如K $_{2}$ O中的$1.87\times10^{4}$ cm $^{2}$ V $^{-1}$ S $^{-1}$）.最引人注目的是，DMMC单层（ML）在价带（VB）边缘附近具有扩展的范霍夫奇点，这可以通过$\sim1.0\times10^{13}$ cm $^{-2}$的适度空穴掺杂容易地获得。一旦达到临界点，DMMC ML经历自发的铁磁转变时，顶部VB成为完全自旋极化的强交换相互作用。这种门可调磁性在DMMC ML是有前途的探索新的器件概念在自旋电子学，电子学和光电子学。
英文摘要：
The discovery of archetypal two-dimensional (2D) materials provides enormous opportunities in both fundamental breakthroughs and device applications, as evident by the research booming in graphene, atomically thin transition-metal chalcogenides, and few-layer black phosphorous in the past decade. Here, we report a new, large family of semiconducting dialkali-metal monochalcogenides (DMMCs) with an inherent A$_{2}$X monolayer structure, in which two alkali sub-monolayers form hexagonal close packing and sandwich the triangular chalcogen atomic plane. Such unique lattice structure leads to extraordinary physical properties, such as good dynamical and thermal stability, visible to near-infrared light energy gap, high electron mobility (e.g. $1.87\times10^{4}$ cm$^{2}$V$^{-1}$S$^{-1}$ in K$_{2}$O). Most strikingly, DMMC monolayers (MLs) host extended van Hove singularities near the valence band (VB) edge, which can be readily accessed by moderate hole doping of $\sim1.0\times10^{13}$ cm$^{-2}$. Once the critical points are reached, DMMC MLs undergo spontaneous ferromagnetic transition when the top VBs become fully spin-polarized by strong exchange interactions. Such gate tunable magnetism in DMMC MLs are promising for exploring novel device concepts in spintronics, electronics and optoelectronics.
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