University of Tsukuba Faculty of Pure and Applied Sciences Associate Professor Takahiro Kondo and Professor Junji Nakamura, in cooperation with Researcher Donghui Guo and Professor Susumu Okada of the same faculty, have shown from detailed measurements that in atomically flat areas of a nitrogen-doped graphite surface in the absence of external magnetic fields, Landau levels manifest corresponding to super strong magnetic fields of approximately 100 tesla across bilayer graphene.

There has been some debate thus far that the source of Landau levels generated under non-magnetic fields has been pseudo-magnetic fields induced by asymmetries, but in this study the researchers observed Landau levels on atomically flat surfaces without asymmetries, showing for the first time the existence of Landau levels generated by sources other than asymmetries. These results further endorse the "domain model" (the mechanism for Landau level generation under a non-magnetic field) that this same research team has advocated for in the past, and newly reveals the unique properties of graphite-based carbon materials such as graphene, which could be used as new materials in electronic devices or for catalysis.

Graphite-based carbon materials such as graphene exhibit powerful electrical conductivity and excellent strength in small quantities, so there is hope that they may contribute to next-generation materials in a variety of fields. The discovery of new physical properties of carbon materials in this study could lead to new applications in environmental materials like electronic materials that make use of electronic state controls such as band gap controls, catalysts, or batteries.

Domain is formed by on-site potential differences around graphitic N. (a) Schematic image of the nitrogen-doped graphite surface, where graphitic N is located at the centre positions indicated by arrows. It is atomically flat and there is no large corrugation. (b) Schematic image of the on-site potential of carbon at the surface modelled in (a). The domain with the higher potential is surrounded by graphitic N, as indicated by the arrow. (c) Schematic image of equipotential contours at the surface modelled in (a).

Original Paper

Takahiro Kondo, Donghui Guo, Taishi Shikano, Tetsuya Suzuki, Masataka Sakurai, Susumu Okada1 & Junji Nakamura, Observation of Landau levels on nitrogen-doped flat graphite surfaces without external magnetic fields, Scientific Reports　5, 16412 (2015).
DOI: 10.1038/srep16412