标题： 电场诱导的二维铁磁Janus VSSe双层中的半金属特性 显示英文标题

标题： Electric-field induced half-metallicity in a two-dimensional ferromagnetic Janus VSSe bilayer

摘要： 二维(2D)半金属具有内在的铁磁性，在自旋电子学中具有广阔的应用前景。 在本研究中，我们旨在通过研究Janus VSSe双层来扩展已知的这种二维铁磁(FM)半金属空间，它是一种FM半导体。 其结构、电子和磁性特性使用密度泛函理论进行研究，采用DFT+$U$方法，并结合PBE泛函。 在最高400 K的有限温度下，使用从头算分子动力学模拟来检查双层的稳定性。为了进一步确保稳定性，还研究了系统的弹性常数，我们发现VSSe双层表现出类似于其单层 counterparts 的易磁化平面。 在DFT+$U$水平下，所考虑的VSSe双层呈现出向半金属转变的趋势，多数自旋载流子的带隙为0.11 eV，而少数自旋载流子的带隙为0.66 eV。 为了包括从半导体到半金属的转变，双层被施加了不同强度的垂直于平面的外部电场。 由于双层缺乏水平镜像对称性，可以双向调节带隙，对于"向上"和"向下"方向的电场有不同的值。 两个自旋通道的带隙随着向上电场的增加而增加，而对于向下电场则相反，多数载流子带隙在0.16 V/$\unicode{x212B}$时关闭，使材料成为自旋无带隙半导体。 电场进一步增加使材料在0.18 V/$\unicode{x212B}$时变为半金属。 考虑到这些外部电场的值在实验室中是可实现的，这表明FM Janus VSSe双层是自旋电子器件的有前途的候选材料。 显示英文摘要

摘要： Two-dimensional (2D) half-metals with intrinsic ferromagnetism hold great potential for applications in spintronics. In this study, we aim to expand the known space of such 2D ferromagnetic (FM) half-metals by investigating bilayer of Janus VSSe, an FM semiconductor. Its structural, electronic, and magnetic properties are examined using density functional theory, employing the DFT+$U$ method, coupled with the PBE functional. The stability of the bilayer is examined using ab initio molecular dynamics simulations at finite temperatures up to 400 K. To ensure the stability further, the elastic constants of the system have also been investigated and we found that VSSe bilayer manifests an easy plane of magnetization similar to its monolayer counterpart. At the DFT+$U$ level, the considered VSSe bilayer exhibits a tendency towards half-metallicity with a small band gap of 0.11 eV for the majority spin carriers, and of 0.66 eV for the minority ones. To include a transition from a semiconductor to a half-metal, the bilayer is subjected to an external electric field of varying strengths normal to the plane. The lack of horizontal mirror symmetry in the bilayer allows bidirectional tuning of the band gap, with different values for the field in "upward" and "downward" directions. The band gaps for the two spin channels increase with the increasing upward electric field, while the opposite happens for the downward fields, with the majority carrier gap closing at 0.16 V/$\unicode{x212B}$, making the material a spin gapless semiconductor. Further increase in the electric field renders the material half metallic at 0.18 V/$\unicode{x212B}$. Given the fact that these values of the external electric field are achievable in the lab suggests that the FM Janus VSSe bilayer is a promising candidate for spintronic devices.