论文标题
稀有地球2H-GDIBR单层的二维铁磁半导体，具有较大的山谷极化
Two-dimensional ferromagnetic semiconductors of rare-earth Janus 2H-GdIBr monolayer with large valley polarization
论文作者
论文摘要
基于通过第一原理计算的稀有地球GD原子，我们证明Janus 2H-GDIBR单层具有固有的铁磁（FM）半导体特征，其间接带隙为0.75 ev，高curie温度t $ _ {C c} $ _ {C c} $ _ {c} $ 260 $ 260 k，80 $μ_{b} $/f.u。 （F.U. =配方单元），面内磁各向异性（IMA）和118 MEV的大型自发谷极化。 MAE，原子间距离或角度以及T $ _ {C} $可以通过面内应变和电荷载体掺杂有效调节。在应变范围内从$ -5％到5％，收费从$ - $ 0.3E到0.3e/f.u。掺杂量，该系统仍然保持FM订购，相应的T $ _ {C} $可以通过233 k的压力从233 K到281 K到281 K到281 k，并且通过电荷载载载掺杂从140 k到245 k。 （$ d_ {z^{2}} $，$ d_ {yz} $），（$ d_ {x^{2} -y^{2}} $，$ d_ {xy} $）和（$ p_ {x} $，$ p_ {y} $ gd at of gd Atom doction the Mae docration the Mae Privation intornation the Mae Privation intornation noctions to and Stridate intorgation to nournation the Martinate with with with with with with Inconty with with with GD- $ D $，GD-$ P $轨道和基于二阶扰动理论的卤素原子的$ P $轨道。由于janus 2H-GDibr单层中的时间反转对称性破裂，不等的狄拉克山谷并非充满活力的退化。 K和K $^{\ prime} $点的浆果曲率之间的一个相当大的山谷差距为有选择性地控制山谷自由并操纵异常大厅效应提供了机会。外部拉伸（压缩）应变进一步增加（减小）山谷缝隙最大值（最小）值为158（37）MEV，这表明Janus 2H-GDIBR单层中的山谷极化对外部菌株具有强大的稳定性。
Based on a rare-earth Gd atom with 4$f$ electrons, through first-principles calculations, we demonstrate that the Janus 2H-GdIBr monolayer exhibits an intrinsic ferromagnetic (FM) semiconductor character with an indirect band gap of 0.75 eV, high Curie temperature T$_{c}$ of 260 K, significant magnetic moment of 8 $μ_{B}$/f.u. (f.u.=formula unit), in-plane magnetic anisotropy (IMA) and large spontaneous valley polarization of 118 meV. The MAE, inter-atomic distance or angle, and T$_{c}$ can be efficiently modulated by in-plane strains and charge carrier doping. Under the strain range from $-$5% to 5% and charge carrier doping from $-$0.3e to 0.3e/f.u., the system still remains FM ordering and the corresponding T$_{c}$ can be modulated by strains from 233 K to 281 K and by charge carrier doping from 140 K to 245 K. Interestingly, under various strains, the matrix elements differences ($d_{z^{2}}$, $d_{yz}$), ($d_{x^{2}-y^{2}}$, $d_{xy}$) and ($p_{x}$, $p_{y}$) of Gd atoms dominate the MAE behaviors, which originates from the competition between the contributions of Gd-$d$, Gd-$p$ orbitals, and $p$ orbitals of halogen atoms based on the second-order perturbation theory. Inequivalent Dirac valleys are not energetic degenerate due to the time-reversal symmetry breaking in the Janus 2H-GdIBr monolayer. A considerable valley gap between the Berry curvature at the K and K$^{\prime}$ points provides an opportunity to selectively control the valley freedom and to manipulate the anomalous Hall effect. External tensile (compressive) strain further increases (decreases) the valley gap up to a maximum (minimum) value of 158 (37) meV, indicating that the valley polarization in the Janus 2H-GdIBr monolayer is robust to the external strains.
