Anomalous Hall effect at half filling in twisted bilayer graphene
Anomalous Hall effect at half filling in twisted bilayer graphene
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DOI：
10.1038/s41567-022-01697-7
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发表时间：
2022-02
期刊：
影响因子：
19.6
通讯作者：
C. Tseng;Xu-Fei Ma;Zhaoyu Liu;Kenji Watanabe;T. Taniguchi;J. Chu;M. Yankowitz
中科院分区：
文献类型：
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作者：
C. Tseng;Xu-Fei Ma;Zhaoyu Liu;Kenji Watanabe;T. Taniguchi;J. Chu;M. Yankowitz
魔角扭曲双层石墨烯（tBLG）具有多种破缺相、关联的陈氏绝缘体、轨道磁性和超导性，，-。特别是，当能带中每个莫尔晶胞中填充有奇数个电子时，观察到了反常的霍尔效应，表明出现了具有自发破缺的时间反转对称性的零场轨道磁态。在这里，我们提出了两个tBLG设备的扭转角稍微远离魔角的测量和报告的异常霍尔效应在半填充的电子和空穴莫尔带的观察。我们认为，两个因素增加的能带色散远离魔角，和基板电位从封装氮化硼可能发挥关键作用，在稳定的谷极化基态在半填充。我们的研究结果进一步扩大了丰富的相关相图tBLG，并表明需要制定一个更完整的了解其流形的密切竞争的破坏秩序。
Magic-angle twisted bilayer graphene (tBLG) displays a variety of symmetry-broken phases, correlated Chern insulators, orbital magnetism and superconductivity, , , , , , –. In particular, the anomalous Hall effect has been observed when the bands are filled with an odd number of electrons per moiré unit cell,,, indicating the emergence of a zero-field orbital magnetic state with spontaneously broken time-reversal symmetry, –. Here we present measurements of two tBLG devices with twist angles slightly away from the magic angle and report the observation of the anomalous Hall effect at half filling of both the electron and hole moiré bands. We suggest that two factors—the increased band dispersion away from the magic angle, and substrate potentials from the encapsulating boron nitride—probably play critical roles in stabilizing a valley-polarized ground state at half filling. Our findings further expand the rich correlated phase diagram of tBLG, and indicate the need to develop a more complete understanding of its manifold of closely competing symmetry-breaking orders.