AI 中文总结
通过第一性原理计算，发现III族元素取代可调控碲封装硅烯衍生的\textbf{\textit{Si2X2Te2}}单分子层的电子结构，其中\textbf{\textit{Si2In2Te2}}为候选量子自旋霍尔绝缘体，实现了拓扑性质的转变。
AI 中文摘要
我们采用第一性原理计算研究二维\textbf{\textit{Si2X2Te2}}（\textbf{\textit{X}} = \textbf{\textit{B}}、\textbf{\textit{Al}}、\textbf{\textit{Ga}}和\textbf{\textit{In}}）单分子层的电子、光学及拓扑性质的化学调控。所有化合物均为动态稳定的半导体，其振动与电子性质随III族元素取代呈系统性演化。包含自旋-轨道耦合的杂化泛函计算显示，其带边以\textbf{\textit{p}}轨道为主，且从B到In的相对论效应逐渐增强。最值得注意的是，计算得到的\textbf{\textit{Z2}}不变量表明，\textbf{\textit{Si2In2Te2}}是候选的量子自旋霍尔绝缘体，而基于B、Al、Ga的单分子层仍为拓扑平庸态。Bethe-Salpeter计算进一步显示，电子-空穴相互作用会重新分配吸收阈值附近的振子强度，同时保持弱面内光学各向异性。我们的研究确立了III族元素取代作为一种简单的化学途径，可调控\textbf{\textit{Si2X2Te2}}单分子层的电子结构，并驱动其从拓扑平庸态向非平庸拓扑态的转变。
英文摘要
We investigate chemical control of the electronic, optical, and topological properties of two-dimensional \ce{Si2X2Te2} (\ce{X} = \ce{B}, \ce{Al}, \ce{Ga}, and \ce{In}) monolayers using first-principles calculations. All compounds are dynamically stable semiconductors, with their vibrational and electronic properties evolving systematically upon group-III substitution. Hybrid-functional calculations including spin--orbit coupling reveal predominantly $p$-orbital band edges and increasingly pronounced relativistic effects from B to In. Most notably, the calculated $\mathbb{Z}_2$ invariant identifies \ce{Si2In2Te2} as a candidate quantum spin Hall insulator, while the B-, Al-, and Ga-based monolayers remain topologically trivial. Bethe--Salpeter calculations further show that electron--hole interactions redistribute oscillator strength near the absorption onset while preserving a weak in-plane optical anisotropy. Our results establish group-III substitution as a simple chemical route to tune the electronic structure and drive a transition from trivial to nontrivial topology in \ce{Si2X2Te2} monolayers.
