Yang Juntao, Zhou Yong, Guo Qilin, Dedkov Yuriy, Voloshina Elena
Department of Physics, Shanghai University 99 Shangda Road 200444 Shanghai P. R. China
School of Science, Hubei University of Automotive Technology 167 Checheng West Road Shiyan City 442002 Hubei P. R. China.
RSC Adv. 2020 Jan 2;10(2):851-864. doi: 10.1039/c9ra09030d.
Based on density functional theory (DFT), we performed first-principles studies on the electronic structure, magnetic state and optical properties of two-dimensional (2D) transition-metal phosphorous trichalcogenides MnPX (X = S and Se). The calculated interlayer cleavage energies of the MnPX monolayers indicate the energetic possibility to be exfoliated from the bulk phase, with good dynamical stability confirmed by the absence of imaginary contributions in the phonon spectra. The MnPX monolayers are both Néel antiferromagnetic (AFM) semiconductors with direct band gaps falling into the visible optical spectrum. Magnetic interaction parameters were extracted within the Heisenberg model to investigate the origin of the AFM state. Three in-plane magnetic exchange parameters play an important role in the robust AFM configuration of Mn ions. The Néel temperatures ( ) were estimated by means of Monte Carlo simulations, obtaining theoretical values of 103 K and 80 K for 2D MnPS and MnPSe, respectively. With high spin state Mn ions arranged in honeycomb lattices, the spin-degenerated band structures exhibit valley polarisation and were investigated in different biaxial in-plain strains, considering the spin-orbital coupling (SOC). 2D MnPX monolayers show excellent performance in terms of the optical properties, and the absorption spectra were discussed in detail to find the transition mechanism. Different amounts and configurations of chalcogen vacancies were introduced into the MnPX monolayers, and it was found that the electronic structures are heavily affected depending on the vacancy geometric structure, leading to different magnetic state and absorption spectra of defected MnPX systems.
基于密度泛函理论（DFT），我们对二维（2D）过渡金属三硫属磷化物MnPX（X = S和Se）的电子结构、磁态和光学性质进行了第一性原理研究。计算得到的MnPX单层的层间解离能表明从体相剥离的能量可能性，声子谱中没有虚部贡献证实了其具有良好的动力学稳定性。MnPX单层都是奈尔反铁磁（AFM）半导体，其直接带隙落入可见光光谱范围内。在海森堡模型中提取磁相互作用参数以研究AFM态的起源。三个面内磁交换参数在Mn离子的稳健AFM构型中起重要作用。通过蒙特卡罗模拟估计了奈尔温度（ ），得到二维MnPS和MnPSe的理论 值分别为103 K和80 K。对于排列在蜂窝晶格中的高自旋态Mn离子，考虑自旋轨道耦合（SOC），研究了自旋简并能带结构在不同双轴面内应变下的谷极化情况。二维MnPX单层在光学性质方面表现出色，并详细讨论了吸收光谱以找到跃迁机制。在MnPX单层中引入了不同数量和构型的硫属空位，发现电子结构会根据空位几何结构受到严重影响，并导致缺陷MnPX系统具有不同的磁态和吸收光谱。
