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arXiv · 1804.04261

Dirac Electrons in a Dodecagonal Graphene Quasicrystal

Sung Joon Ahn·Pilkyung Moon·Tae-Hoon Kim·Hyun-Woo Kim·Ha-Chul Shin·Eun Hye Kim·Hyun Woo Cha·Se-Jong Kahng·Philip Kim·Mikito Koshino·Young-Woo Son·Cheol-Woong Yang·Joung Real Ahn
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Abstract

Quantum states of quasiparticles in solids are dictated by symmetry. Thus, a discovery of unconventional symmetry can provide a new opportunity to reach a novel quantum state. Recently, Dirac and Weyl electrons have been observed in crystals with discrete translational symmetry. Here we experimentally demonstrate Dirac electrons in a two-dimensional quasicrystal without translational symmetry. A dodecagonal quasicrystal was realized by epitaxial growth of twisted bilayer graphene rotated exactly 30 degree. The graphene quasicrystal was grown up to a millimeter scale on SiC(0001) surface while maintaining the single rotation angle over an entire sample and was successfully isolated from a substrate, demonstrating its structural and chemical stability under ambient conditions. Multiple Dirac cone replicated with the 12-fold rotational symmetry were observed in angle resolved photoemission spectra, showing its unique electronic structures with anomalous strong interlayer coupling with quasi-periodicity. Our study provides a new way to explore physical properties of relativistic fermions with controllable quasicrystalline orders.

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Sung Joon Ahn, Pilkyung Moon, Tae-Hoon Kim, Hyun-Woo Kim, Ha-Chul Shin, Eun Hye Kim, Hyun Woo Cha, Se-Jong Kahng, Philip Kim, Mikito Koshino, Young-Woo Son, Cheol-Woong Yang, Joung Real Ahn. 2018-04-12. Dirac Electrons in a Dodecagonal Graphene Quasicrystal. https://doi.org/10.1126/science.aar8412

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