Title: Emergence of Diverse Topological States in Ge Doped MnBi2Te4 Show Chinese title

Title: 锗掺杂MnBi2Te4中多种拓扑态的出现

Abstract: As an ideal platform for studying interplays between symmetry, topology and magnetism, the magnetic topological insulator (MTI) MnBi2Te4 has attracted extensive attentions. However, its strong n-type intrinsic defects hinder the realizations of exotic phenomena. Stimulated by recent discoveries that Ge doping can efficiently tune the position of Fermi level, here we systematically investigate the band evolution and topological phase diagram with doping concentration from MTI MnBi2Te4 to strong topological insulator GeBi2Te4. Different from magnetically doped Bi2Se3, the topology here is determined by competition of two band inversions arising from band folding of two time-reversal invariant momenta between antiferromagnetic and nonmagnetic/ferromagnetic unit cells. By employing a band momentum mapping method, besides the known MTI phase, remarkably, we find two classes of magnetic Dirac semimetal phases at antiferromagnetic state, two classes of Weyl semimetal phases at ferromagnetic state, and an intermediate trivial state at different doping regions. Interestingly, the trivial state can be tuned into a Weyl phase with two coexisting band inversions and extraordinarily long Fermi arcs by a small strain. Our work reveals diverse topological states with intrinsic quantum phenomena can be achieved with great potential for designing future electronic devices. Show Chinese abstract

Abstract: 作为一种研究对称性、拓扑性和磁性之间相互作用的理想平台，磁性拓扑绝缘体（MTI）MnBi2Te4引起了广泛的关注。然而，其强烈的n型本征缺陷阻碍了奇异现象的实现。受到最近发现的锗（Ge）掺杂可以有效调节费米能级位置的启发，我们系统地研究了从MTI MnBi2Te4到强拓扑绝缘体GeBi2Te4的掺杂浓度下的能带演化和拓扑相图。与磁性掺杂的Bi2Se3不同，这里的拓扑性由反铁磁单元和非磁性/铁磁性单元之间两个时间反演不变动量之间的能带折叠引起的两种能带反转的竞争决定。通过采用能带动量映射方法，除了已知的MTI相外，我们惊奇地发现了两种反铁磁状态下磁性狄拉克半金属相，两种铁磁状态下外尔半金属相，以及不同掺杂区域的一个中间平凡态。有趣的是，通过微小的应变，平凡态可以被调整为具有两个共存能带反转和异常长的费米弧的外尔相。我们的工作揭示了具有内在量子现象的多种拓扑状态可以通过设计未来电子器件的巨大潜力来实现。