三斜晶系RhBi2中弱拓扑绝缘态和范霍夫奇异性的发现
Discovery of a weak topological insulating state and van Hove singularity in triclinic RhBi2
摘要：
时反对称不变性拓扑绝缘体是拓扑材料领域的典范，是拓扑材料发展的起点。除了TRS保护的“强”TI之外，人们很早就认识到存在更多混淆的弱拓扑绝缘体（WTI）。WTI依赖于平移对称性，并且仅在某些方向上表现出拓扑表面状态，这使得与强TI的实验成功相匹配变得更加困难。我们在这里报告发现的WTI状态RhBi 2属于最佳空间群P1，这是唯一的空间群，其中对称性表明本征值枚举所有可能的不变量，由于没有额外的约束晶体对称性。我们的ARPES，DFT计算和有效模型揭示了拓扑表面态的鞍点位于附近的狄拉克点，导致沿（100）方向接近费米能的范霍夫奇点（VHS）。由于奇异特性的结合，这种材料提供了巨大的潜力，作为一种新的量子效应的材料平台。
英文摘要：
Time reversal symmetric (TRS) invariant topological insulators (TIs) fullfil a paradigmatic role in the field of topological materials, standing at the origin of its development. Apart from TRS protected 'strong' TIs, it was realized early on that more confounding weak topological insulators (WTI) exist. WTIs depend on translational symmetry and exhibit topological surface states only in certain directions making it significantly more difficult to match the experimental success of strong TIs. We here report on the discovery of a WTI state in RhBi2 that belongs to the optimal space group P1, which is the only space group where symmetry indicated eigenvalues enumerate all possible invariants due to absence of additional constraining crystalline symmetries. Our ARPES, DFT calculations, and effective model reveal topological surface states with saddle points that are located in the vicinity of a Dirac point resulting in a van Hove singularity (VHS) along the (100) direction close to the Fermi energy. Due to the combination of exotic features, this material offers great potential as a material platform for novel quantum effects.
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