Quasicrystal is an unusual structure of solid that was first experimentally observed in the 1980s by Nobel Laureate Dan Shechtman. In a typical solid, the constituent elements are arranged with a certain periodicity called a lattice structure, and in this case, it has both translational and rotational symmetry. However, quasicrystals have a distinct structure with only rotational symmetry, and have fractal structure with self-similarity.

In addition, there have been many theoretical and experimental studies on the interaction between two graphene layers, but unusual physical phenomena such as Mott insulator and superconducting phenomenon have been reported in the academic community until recently. We have recently published a study on two-dimensional quasicrystal using two graphene layers in accordance with these research trends.

In this study, instead of stacking of separated two graphene layers, two-dimensional graphene quasicrystals could be synthesized by epitaxially growing two graphene layers having a rotation angle of 30 degrees. Then we first discovered a special quasicrystal with Dirac Fermions. The synthesized graphene quasicrystals were confirmed to have 12-fold symmetry and fractal structure which are not seen in general crystal structure as shown in the attached figure. It is expected that the physics in 4-dimensional space represented by 4D quantum Hall effect can be observed through this two-dimensional graphene quasicrystal.

This research was published in Science on August 24, 2018 and was selected as a cover paper.

Science 24 Aug 2018: