Owing to their unique topologically protected gapless boundary states, topological insulators (TIs) are attracting substantial interest in spintronics and quantum computing. Here, we discuss the structural, electronic, and topological properties of bulk alkaline earth di-pnictides AX2 (where A= Ca, Sr, or Ba and X= As, Sb, or Bi) using first-principles calculations under the hybrid functional approach. Our structural analysis based on phonon dispersion and molecular dynamics calculations establishes the thermodynamic stability of these materials and indicates their potential for synthesis. All investigated compounds are shown to host nontrivial phases upon including spin–orbit coupling. CaAs2, SrSb2, and BaSb2 are found to be strong TIs with sizable bandgaps of up to 213 meV. Nontrivial topology in the case of SrSb2 was further confirmed through surface state computations which showed the presence of gapless surface states. In addition, we demonstrate that using the hybrid functional approach can enhance the accuracy of the calculations to predict experimental findings. Finally, our study suggests that the alkaline earth di-pnictide family would provide a promising materials platform for developing applications of TIs.

中文翻译：

---

非同型体 AX2（A = Ca、Sr 或 Ba;X = As、Sb 或 Bi）化合物中的拓扑绝缘相


由于其独特的拓扑保护无间隙边界态，拓扑绝缘体 （TI） 正在吸引人们对自旋电子学和量子计算的浓厚兴趣。在这里，我们使用混合泛函方法下的第一性原理计算讨论了体碱土二氯化物 AX2 （其中 A= Ca、Sr 或 Ba 和 X= As、Sb 或 Bi） 的结构、电子和拓扑性质。我们基于声子分散和分子动力学计算的结构分析确定了这些材料的热力学稳定性，并表明了它们的合成潜力。所有研究的化合物在包括自旋-轨道耦合时都显示出非平凡相。发现 CaAs2、SrSb2 和 BaSb2 是强 TI，具有高达 213 meV 的相当大的带隙。SrSb2 情况下的非平凡拓扑结构通过表面状态计算得到进一步证实，该计算表明存在无间隙表面状态。此外，我们证明使用混合函数方法可以提高预测实验结果的计算准确性。最后，我们的研究表明，碱土二镍矿家族将为开发 TIs 的应用提供一个有前途的材料平台。