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arXiv 1012.0460cond-mat.mes-hall
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公度石墨烯旋转堆积中的对称性破缺:理论与实验的比较

Symmetry breaking in commensurate graphene rotational stacking; a comparison of theory and experiment

J. Hicks, M. Sprinkle, K. Shepperd, F. Wang, A. Tejeda, A. Taleb-Ibrahimi, F. Bertran, P. Le Fèvre, W. A. de Heer, C. Berger, E. H. Conrad

摘要:

以Bernal构型(片之间相对旋转60度)堆叠的石墨烯在电子上不同于孤立的石墨烯,这是由于由两个石墨烯晶胞原子中的仅一个之间形成的层间键引入的对称性破缺。各种各样的实验表明,非伯纳尔旋转恢复了这种对称性的破坏;因此,这些堆叠品种一直是密集的理论兴趣的主题。大多数理论预测能带结构的实质性变化,范围从范霍夫奇点的发展和角度相关的电子局域化,导致费米速度变为零,因为片之间的相对旋转角变为零。在这项工作中,我们通过直接测量表明,非Bernal旋转保持石墨烯对称性,由于有效层间耦合弱,只有很小的扰动。我们既没有发现范霍夫奇点,也没有发现费米速度的任何显著变化。这些结果表明,在我们目前的理论理解这种材料的能带结构的起源的重大问题。

英文摘要:

Graphene stacked in a Bernal configuration (60 degrees relative rotations between sheets) differs electronically from isolated graphene due to the broken symmetry introduced by interlayer bonds forming between only one of the two graphene unit cell atoms. A variety of experiments have shown that non-Bernal rotations restore this broken symmetry; consequently, these stacking varieties have been the subject of intensive theoretical interest. Most theories predict substantial changes in the band structure ranging from the development of a Van Hove singularity and an angle dependent electron localization that causes the Fermi velocity to go to zero as the relative rotation angle between sheets goes to zero. In this work we show by direct measurement that non-Bernal rotations preserve the graphene symmetry with only a small perturbation due to weak effective interlayer coupling. We detect neither a Van Hove singularity nor any significant change in the Fermi velocity. These results suggest significant problems in our current theoretical understanding of the origins of the band structure of this material.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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