Wang Weimin, Shi Yuchen, Zakharov Alexei A, Syväjärvi Mikael, Yakimova Rositsa, Uhrberg Roger I G, Sun Jianwu
Department of Physics, Chemistry and Biology (IFM) , Linköping University , SE-58183 , Linköping , Sweden.
MAX IV Laboratory , Fotongatan 2 , SE-22484 , Lund , Sweden.
Nano Lett. 2018 Sep 12;18(9):5862-5866. doi: 10.1021/acs.nanolett.8b02530. Epub 2018 Aug 24.
The stacking order of multilayer graphene significantly influences its electronic properties. The rhombohedral stacking sequence is predicted to introduce a flat band, which has high density of states and the enhanced Coulomb interaction between charge carriers, thus possibly resulting in superconductivity, fractional quantum Hall effect, and many other exotic phases of matter. In this work, we comprehensively study the effect of the stacking sequence and interlayer spacing on the electronic structure of four-layer graphene, which was grown on a high crystalline quality 3C-SiC(111) crystal. The number of graphene layers and coverage were determined by low energy electron microscopy. First-principles density functional theory calculations show distinctively different band structures for ABAB (Bernal), ABCA (rhombohedral), and ABCB (turbostratic) stacking sequences. By comparing with angle-resolved photoelectron spectroscopy data, we can verify the existence of a rhombohedral stacking sequence and a nearly dispersionless electronic band (flat band) near the Fermi level. Moreover, we find that the momentum width, bandgap, and curvature of the flat-band region can be tuned by the interlayer spacing, which plays an important role in superconductivity and many other exotic phases of matter.
多层石墨烯的堆叠顺序对其电子性质有显著影响。据预测，菱面体堆叠序列会引入一个平带，该平带具有高态密度以及电荷载流子之间增强的库仑相互作用，从而可能导致超导性、分数量子霍尔效应以及许多其他奇异的物质相。在这项工作中，我们全面研究了堆叠序列和层间距对在高质量3C - SiC(111)晶体上生长的四层石墨烯电子结构的影响。石墨烯层数和覆盖率通过低能电子显微镜确定。第一性原理密度泛函理论计算表明，ABAB（伯纳尔）、ABCA（菱面体）和ABCB（乱层）堆叠序列具有明显不同的能带结构。通过与角分辨光电子能谱数据比较，我们可以验证菱面体堆叠序列以及费米能级附近几乎无色散的电子能带（平带）的存在。此外，我们发现平带区域的动量宽度、带隙和曲率可以通过层间距进行调节，这在超导性和许多其他奇异物质相中起着重要作用。
