D'Souza Joel, Villaos Rovi Angelo B, Iii Aniceto B Maghirang, Verzola Ina Marie R, Covilakam Sreeparvathy Puthiya, Huang Zhi-Quan, Chuang Feng-Chuan
Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan.
Physics Division, National Center for Theoretical Sciences, Taipei 10617, Taiwan.
ACS Omega. 2025 Apr 10;10(15):15272-15279. doi: 10.1021/acsomega.4c11092. eCollection 2025 Apr 22.
Two-dimensional (2D) materials have emerged as a significant focus in materials research due to their tunable properties on thermoelectricity, spin-splitting, and nontrivial topology. Specifically, Janus-type 2D materials are interesting due to their additional breaking of inversion or mirror symmetry in the atomic structure. Based on the recently synthesized monolayer MoSiN and previously studied BaInTe with the chemical formula of MAZ, we derive a family of 2D Janus compounds, namely BaABTe. Using first-principles calculations, a total of six Janus BaABTe monolayers (BaAlGaTe, BaAlInTe, BaAlTlTe, BaGaInTe, BaGaTlTe, and BaInTlTe) were investigated for their dynamical stability, electronic, and topological properties. Notably, the Z topological invariant calculated using HSE06 hybrid functional reveals that three out of the six monolayers (BaAlGaTe, BaAlTlTe, and BaInTlTe) have nontrivial topological phases, with BaInTlTe exhibiting the largest positive system band gap of 17 meV. These three topological monolayers were further confirmed to be dynamically stable based on phonon dispersion and formation energy calculations. Subsequent orbital analysis of BaInTlTe showed that the spin-orbit coupling effect drives the topological phase transition, resulting in the band inversion between the -orbital of In + Tl and + -orbitals of Te around Γ. Also, the presence of the gapless edge states confirmed the nontrivial topological property. The Janus monolayers were found to exhibit significant Rashba spin-splitting except BaAlInTe. The topologically nontrivial BaAlTlTe has the strongest Rashba strength of α= α = 1.03 eVÅ. Our results show that the coexisting nature of the nontrivial phase and Rashba-type splitting within the BaABTe Janus monolayers might apply to spintronics.
二维（2D）材料因其在热电性、自旋分裂和非平凡拓扑方面的可调谐特性，已成为材料研究的一个重要焦点。具体而言，Janus型二维材料因其原子结构中额外的反演或镜面对称性破缺而备受关注。基于最近合成的单层MoSiN以及先前研究的化学式为MAZ的BaInTe，我们推导出了一族二维Janus化合物，即BaABTe。通过第一性原理计算，总共研究了六个Janus BaABTe单层（BaAlGaTe、BaAlInTe、BaAlTlTe、BaGaInTe、BaGaTlTe和BaInTlTe）的动力学稳定性、电子性质和拓扑性质。值得注意的是，使用HSE06杂化泛函计算的Z拓扑不变量表明，六个单层中的三个（BaAlGaTe、BaAlTlTe和BaInTlTe）具有非平凡拓扑相，其中BaInTlTe表现出最大的正系统带隙，为17 meV。基于声子色散和形成能计算，进一步证实这三个拓扑单层是动力学稳定的。对BaInTlTe的后续轨道分析表明，自旋轨道耦合效应驱动拓扑相变，导致在Γ附近In + Tl的 -轨道与Te的 + -轨道之间的能带反转。此外，无隙边缘态的存在证实了非平凡拓扑性质。发现除BaAlInTe外，Janus单层表现出显著的Rashba自旋分裂。拓扑非平凡的BaAlTlTe具有最强的Rashba强度，α = α = 1.03 eVÅ。我们的结果表明，BaABTe Janus单层中非平凡相和Rashba型分裂的共存性质可能适用于自旋电子学。
