Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Science. 2013 Jun 21;340(6139):1427-30. doi: 10.1126/science.1237240. Epub 2013 May 16.
van der Waals heterostructures constitute a new class of artificial materials formed by stacking atomically thin planar crystals. We demonstrated band structure engineering in a van der Waals heterostructure composed of a monolayer graphene flake coupled to a rotationally aligned hexagonal boron nitride substrate. The spatially varying interlayer atomic registry results in both a local breaking of the carbon sublattice symmetry and a long-range moiré superlattice potential in the graphene. In our samples, this interplay between short- and long-wavelength effects resulted in a band structure described by isolated superlattice minibands and an unexpectedly large band gap at charge neutrality. This picture is confirmed by our observation of fractional quantum Hall states at ± 5/3 filling and features associated with the Hofstadter butterfly at ultrahigh magnetic fields.
范德华异质结构由堆叠原子层薄平面晶体组成，构成了一类新型的人工材料。我们在由单层石墨烯薄片与旋转排列的六方氮化硼衬底耦合而成的范德华异质结构中展示了能带结构工程。层间原子配位数的空间变化导致了碳原子亚晶格对称性的局部破坏和石墨烯中的长程莫尔超晶格势。在我们的样品中，这种短程和长程效应的相互作用导致了能带结构由孤立的超晶格子带描述，并在电荷中性时出现了出乎意料的大带隙。这一图像得到了我们在 ± 5/3 填充时观察到的分数量子霍尔态以及超高磁场下与霍夫斯塔特蝴蝶相关的特征的证实。
