Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing 100081, China.
Nanoscale. 2017 Nov 16;9(44):17405-17414. doi: 10.1039/c7nr05088g.
Blue phosphorene (BP) and gray arsenene (GA), consisting of phosphorus and arsenic atoms in two-dimensional (2D) low-buckled honeycomb lattices, respectively, have received great interest because of their excellent electronic and optoelectronic performances. Here, using first-principles density functional theory, we investigate magneto-optical (MO) Kerr and Faraday effects in BP and GA under hole doping. Ferromagnetic ground states are found in hole-doped monolayer and bilayer BP and GA due to the Stoner electronic instability, which originates from the van Hove singularity of the density of states at the valence band edge. The Kerr and Faraday effects strongly depend on the doping concentration and therefore are electrically controllable by adjusting the number of holes via the gate voltage. The influences of the thin film thickness, spin-polarized direction, and the substrate on the MO effects are further studied. We find that the MO effects are weakened remarkably as the thin film thickness increases and can be negligible more than three single-layers; the MO effects are much more prominent when spin polarization is along the out-of-plane direction and will decrease more than one order of magnitude on turning the spin in the crystal plane; the insulating substrates with small refractive indices are favorable to generate large MO effects and appropriate compressive strains applied on BP and GA due to lattice mismatch with substrates are further beneficial. The MO effects in GA are generally larger than those in BP because the strength of spin-orbit coupling in the arsenic atom is larger than that in the phosphorus atom. Monolayer GA possesses the largest Kerr and Faraday rotation angles, which are comparable to or even larger than those of well-known MO materials such as 3d-transition-metal multilayers and compounds. Our results indicate that BP and GA are a promising material platform for MO device applications.
蓝磷烯 (BP) 和灰砷烯 (GA) 分别由二维 (2D) 低弯曲蜂窝晶格中的磷和砷原子组成，由于其优异的电子和光电性能而受到广泛关注。在这里，我们使用第一性原理密度泛函理论研究了在空穴掺杂下 BP 和 GA 中的磁光 (MO) 克尔和法拉第效应。由于价带边缘态密度的范霍夫奇点，单层和双层 BP 和 GA 中的空穴掺杂导致了 Stoner 电子不稳定性，从而产生了铁磁基态。克尔和法拉第效应强烈依赖于掺杂浓度，因此可以通过栅极电压调节空穴数来进行电控制。进一步研究了薄膜厚度、自旋极化方向和衬底对 MO 效应的影响。我们发现，MO 效应随着薄膜厚度的增加而显著减弱，超过三个单层后可以忽略不计；当自旋极化沿垂直于平面的方向时，MO 效应更为显著，当自旋在晶面内旋转时，MO 效应将降低一个数量级以上；具有小折射率的绝缘衬底有利于产生大的 MO 效应，并且由于与衬底的晶格失配，施加在 BP 和 GA 上的适当压缩应变也有利于产生大的 MO 效应。由于砷原子的自旋轨道耦合强度大于磷原子，因此 GA 中的 MO 效应通常大于 BP 中的 MO 效应。单层 GA 具有最大的克尔和法拉第旋转角，与 3d 过渡金属多层和化合物等知名 MO 材料相当，甚至更大。我们的结果表明，BP 和 GA 是 MO 器件应用的有前途的材料平台。
