论文标题
预测的分子 - 原子层Janus $ \ mathrm {msigen_4} $（m = mo和w）带有rashba旋转分裂和高电子载体的单层
Predicted septuple-atomic-layer Janus $\mathrm{MSiGeN_4}$ (M=Mo and W) monolayers with Rashba spin splitting and high electron carrier mobilities
论文作者
论文摘要
Janus二维（2D）材料由于其非对称性不对称而引起的独特特性，引起了很多关注，这在许多2D系列中已经实现了。在这项工作中，Janus单层是在新的2D $ \ mathrm {ma_2z_4} $ family中通过第一原理计算，$ \ m atrm {mosi_2n_4} $ anders new new new new new 2d。实验（\ TextColor [RGB] {0.00,0.00,1.00} {Science 369，670-674（2020）}）。预测的$ \ mathrm {msigen_4} $（m = mo和w）单层表现出动态，热力学和机械稳定性，它们是间接的带隙半导体。包含自旋轨道耦合（SOC）会产生RASHBA型自旋分裂，该分裂在价带中观察到，与常见的传导带不同。计算的结果表明，由于SOC引起的传导带边缘的山谷极化以及反转对称性破裂。发现$ \ mathrm {msigen_4} $（m = mo和w）单层具有很高的电子迁移率。当应用基础平面中的单轴应变时，都可以观察到平面内和几乎弱的平面外极化。 janus $ \ mathrm {msigen_4} $（m = mo和w）的压电应变系数$ d_ {11} $的值属于$ \ mathrm {msi_2n_4} $（m = mo and w）的值（mathrm {msi_2n_4} $ and y mathrm {mathrm {mge_2n__2n $} $（MONOL）事实证明，应变可以调整价最大值（VBM）和最低传导带的位置，并增强由压缩应变引起的传导带收敛的强度。还发现，拉伸双轴应变可以增强$ \ \ mathrm {msigen_4} $（m = mo和w）单层的$ d_ {11} $，并且压缩应变可以改善$ d_ {31}} $（绝对值）。
Janus two-dimensional (2D) materials have attracted much attention due to possessing unique properties caused by their out-of-plane asymmetry, which have been achieved in many 2D families. In this work, the Janus monolayers are predicted in new 2D $\mathrm{MA_2Z_4}$ family by means of first-principles calculations, $\mathrm{MoSi_2N_4}$ and $\mathrm{WSi_2N_4}$ of which have been synthesized in experiment(\textcolor[rgb]{0.00,0.00,1.00}{Science 369, 670-674 (2020)}). The predicted $\mathrm{MSiGeN_4}$ (M=Mo and W) monolayers exhibit dynamic, thermodynamical and mechanical stability, and they are indirect band-gap semiconductors. The inclusion of spin-orbit coupling (SOC) gives rise to the Rashba-type spin splitting, which is observed in the valence bands, being different from common conduction bands. Calculated results show valley polarization at the edge of the conduction bands due to SOC together with inversion symmetry breaking. It is found that $\mathrm{MSiGeN_4}$ (M=Mo and W) monolayers have high electron mobilities. Both in-plane and much weak out-of-plane piezoelectric polarizations can be observed, when a uniaxial strain in the basal plane is applied. The values of piezoelectric strain coefficient $d_{11}$ of the Janus $\mathrm{MSiGeN_4}$ (M=Mo and W) monolayers fall between those of the $\mathrm{MSi_2N_4}$ (M=Mo and W) and $\mathrm{MGe_2N_4}$ (M=Mo and W) monolayers, as expected. It is proved that strain can tune the positions of valence band maximum (VBM) and conduction band minimum (CBM), and enhance the the strength of conduction bands convergence caused by compressive strain. It is also found that tensile biaxial strain can enhance $d_{11}$ of $\mathrm{MSiGeN_4}$ (M=Mo and W) monolayers, and the compressive strain can improve the $d_{31}$ (absolute values).
