Dirac Electrons in a Dodecagonal Graphene Quasicrystal

TL;DR

This paper reports the experimental discovery of Dirac electrons in a two-dimensional dodecagonal quasicrystal, expanding the understanding of quantum states in non-periodic structures and revealing unique electronic properties.

Contribution

It demonstrates the realization of a large-scale, stable 2D quasicrystal with Dirac electrons, a novel achievement in materials science and condensed matter physics.

Findings

Dirac cones observed with 12-fold rotational symmetry

Successful growth of a millimeter-scale quasicrystal on SiC

Strong interlayer coupling with quasi-periodic electronic structure

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.