Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland.
Department of Physics, University of Texas at Austin, Austin, TX 78712, USA.
Science. 2021 Sep 10;373(6560):1257-1260. doi: 10.1126/science.abc3534. Epub 2021 Sep 9.
When twisted to angles near 1°, graphene multilayers provide a window on electron correlation physics. Here, we report the discovery of a correlated electron-hole state in double-bilayer graphene twisted to 2.37°. At this angle, the moiré states retain much of their isolated bilayer character, allowing their bilayer projections to be separately controlled by gates. We use this property to generate an energetic overlap between narrow isolated electron and hole bands with good nesting properties. Our measurements reveal the formation of ordered states with reconstructed Fermi surfaces, consistent with a density-wave state. This state can be tuned without introducing chemical dopants, enabling studies of correlated electron-hole states and their interplay with superconductivity.
当扭曲角度接近 1°时，多层石墨烯为研究电子相关物理提供了一个窗口。在这里，我们报告了在扭曲角度为 2.37°的双层石墨烯中发现的关联电子-空穴态。在这个角度下，莫尔态保留了其双层特征的大部分，允许通过门分别控制其双层投影。我们利用这一特性在具有良好嵌套特性的窄孤立电子和空穴带之间产生能量重叠。我们的测量结果揭示了具有重构费米表面的有序态的形成，与密度波态一致。这种状态可以在不引入化学掺杂剂的情况下进行调节，从而能够研究关联电子-空穴态及其与超导性的相互作用。
