Yu Hongyi, Chen Mingxing, Yao Wang
Department of Physics, University of Hong Kong, Hong Kong, China.
School of Physics and Electronics, Hunan Normal University, Changsha 410081, China.
Natl Sci Rev. 2020 Jan;7(1):12-20. doi: 10.1093/nsr/nwz117. Epub 2019 Aug 13.
When quasiparticles move in condensed matters, the texture of their internal quantum structure as a function of position and momentum can give rise to Berry phases that have profound effects on the material's properties. Seminal examples include the anomalous Hall and spin Hall effects from the momentum-space Berry phases in homogeneous crystals. Here, we explore a conjugate form of the electron Berry phase arising from the moiré pattern: the texture of atomic configurations in real space. In homobilayer transition metal dichalcogenides, we show that the real-space Berry phase from moiré patterns manifests as a periodic magnetic field with magnitudes of up to hundreds of Tesla. This quantity distinguishes moiré patterns from different origins, which can have an identical potential landscape, but opposite quantized magnetic flux per supercell. For low-energy carriers, the homobilayer moirés realize topological flux lattices for the quantum-spin Hall effect. An interlayer bias can continuously tune the spatial profile of the moiré magnetic field, whereas the flux per supercell is a topological quantity that can only have a quantized jump observable at a moderate bias. We also reveal the important role of the non-Abelian Berry phase in shaping the energy landscape in small moiré patterns. Our work points to new possibilities to access ultra-high magnetic fields that can be tailored to the nanoscale by electrical and mechanical controls.
当准粒子在凝聚态物质中移动时，其内部量子结构随位置和动量变化的纹理会产生贝里相位，这对材料的性质有深远影响。经典例子包括均匀晶体中动量空间贝里相位导致的反常霍尔效应和自旋霍尔效应。在此，我们探索由莫尔条纹产生的电子贝里相位的共轭形式：实空间中原子构型的纹理。在同质双层过渡金属二硫属化物中，我们表明莫尔条纹产生的实空间贝里相位表现为大小高达数百特斯拉的周期性磁场。这个量区分了不同起源的莫尔条纹，它们可能具有相同的势能景观，但每个超胞的量子化磁通量相反。对于低能载流子，同质双层莫尔条纹实现了量子自旋霍尔效应的拓扑通量晶格。层间偏压可以连续调节莫尔磁场的空间分布，而每个超胞的通量是一个拓扑量，只有在适度偏压下才会有量子化跳跃。我们还揭示了非阿贝尔贝里相位在塑造小莫尔条纹能量景观中的重要作用。我们的工作指出了通过电学和机械控制获得可定制到纳米尺度的超高磁场的新可能性。
