Max-Planck-Institut für Festköperforschung, Stuttgart, Germany.
Phys Rev Lett. 2011 Nov 18;107(21):216602. doi: 10.1103/PhysRevLett.107.216602. Epub 2011 Nov 16.
We address the quantum Hall behavior in twisted bilayer graphene transferred from the C face of SiC. The measured Hall conductivity exhibits the same plateau values as for a commensurate Bernal bilayer. This implies that the eightfold degeneracy of the zero energy mode is topologically protected despite rotational disorder as recently predicted. In addition, an anomaly appears. The densities at which these plateaus occur show a magnetic field dependent offset. It suggests the existence of a pool of localized states at low energy, which do not count towards the degeneracy of the lowest band Landau levels. These states originate from an inhomogeneous spatial variation of the interlayer coupling.
我们研究了从碳化硅 C 面转移过来的扭曲双层石墨烯中的量子霍尔行为。测量得到的霍尔电导率表现出与合宜的 Bernal 双层相同的平台值。这表明,尽管最近预测存在旋转无序,但零能模的八重简并是拓扑保护的。此外,还出现了一个异常现象。这些平台出现的密度表现出与磁场有关的偏移。这表明在低能存在一个局域态的集合,它们对最低能带朗道能级的简并没有贡献。这些态来源于层间耦合的非均匀空间变化。