Topological electrons in semimetals are usually vulnerable to chemical doping and environment change, which restricts their potential application in future electronic devices. In this paper, we report that the type-II Dirac semimetal VAl3 hosts exceptional, robust topological electrons which can tolerate extreme change of chemical composition. The Dirac electrons remain intact, even after a substantial part of V atoms have been replaced in the V1−xTixAl3 solid solutions. This Dirac semimetal state ends at x=0.35, where a Lifshitz transition to p-type trivial metal occurs. The V–Al bond is completely broken in this transition as long as the bonding orbitals are fully depopulated by the holes donated from Ti substitution. In other words, the Dirac electrons in VAl3 are protected by the V–Al bond, whose molecular orbital is their bonding gravity center. Our understanding on the interrelations among electron count, chemical bond, and electronic properties in topological semimetals suggests a rational approach to search robust, chemical-bond-protected topological materials.

半金属中的拓扑电子通常容易受到化学掺杂和环境变化的影响，这限制了它们在未来电子设备中的潜在应用。在本文中，我们报告了II型狄拉克半金属V一种升3拥有异常强大的拓扑电子，可以耐受化学成分的极端变化。即使在V原子中的大部分V原子被取代后，狄拉克电子也保持完整。V1个-XŤ一世X一种升3固溶体。该狄拉克半金属态终止于X=0.35，其中发生Lifshitz过渡到p型琐碎金属。只要结合轨道完全被Ti替代产生的空穴所填充，V-Al键就在这个过渡中被完全破坏。换句话说，狄拉克电子在V一种升3受V–Al键保护，其分子轨道是其键合重心。我们对拓扑半金属中电子数，化学键和电子性质之间的相互关系的理解提出了一种合理的方法来搜索坚固的，受化学键保护的拓扑材料。