论文标题
Chern绝缘子和拓扑平面型魔法扭曲的双层石墨烯
Chern Insulators and Topological Flat-bands in Magic-angle Twisted Bilayer Graphene
论文作者
论文摘要
魔法角扭曲的双层石墨烯（MA-TBG）表现出令人着迷的量子相变，当其平坦波段部分被部分填充时，由增强的电子电子相互作用触发。但是，在很大程度上尚未探索阶段本身以及它们与平坦频带的假定非平凡拓扑结构的联系。在这里，我们报告了传输测量值，揭示了一系列掺杂引起的LIFSHITZ过渡，这些转变伴随着Van Hove奇异性（VHS），这些转变促进了相关诱导的间隙和拓扑上的非平凡的子频带的出现。在存在磁场的情况下，填充1、2、3个载体时，每个Moiré-cell的载体均显示了子频段拓扑，并发出了用Chern-numbers的Chern绝缘子出现的信号！ =！，！，！，！出乎意料的是，对于超过5T的磁场，我们观察到3.5的VHS，这表明有可能具有分数Chern绝缘子的可能性。该VHS伴随着从低温金属到高温绝缘行为的跨界，这是熵驱动的Pomeranchuk样过渡的特征，
Magic-angle twisted bilayer graphene (MA-TBG) exhibits intriguing quantum phase transitions triggered by enhanced electron-electron interactions when its flat-bands are partially filled. However, the phases themselves and their connection to the putative non-trivial topology of the flat bands are largely unexplored. Here we report transport measurements revealing a succession of doping-induced Lifshitz transitions that are accompanied by van Hove singularities (VHS) which facilitate the emergence of correlation-induced gaps and topologically non-trivial sub-bands. In the presence of a magnetic field, well quantized Hall plateaus at filling of 1, 2, 3 carriers per moiré-cell reveal the sub-band topology and signal the emergence of Chern insulators with Chern-numbers, ! = !, !, !, respectively. Surprisingly, for magnetic fields exceeding 5T we observe a VHS at a filling of 3.5, suggesting the possibility of a fractional Chern insulator. This VHS is accompanied by a crossover from low-temperature metallic, to high-temperature insulating behavior, characteristic of entropically driven Pomeranchuk-like transitions,
