期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2020
卷号：117
期号：27
页码：15517-15523
DOI：10.1073/pnas.1917697117
出版社：The National Academy of Sciences of the United States of America
摘要：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 V A l 3 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 V 1 − x T i x A l 3 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 V A l 3 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.
关键词：Dirac electron ; Lifshitz transition ; electron count ; chemical bond
