INSTITUTE OF APPLIED PHYSICS - IAP - physicists characterize properties of photonic graphene

IAP - physicists characterize properties of photonic graphene

Due to its unique structure graphene is ideal not only as a conductor of electricity, but can also be used as coating for packaging and protective covers, or as a laser medium and in detectors. However, crucial for practical use is to determine the electronic properties of the extraordinary material precisely. This was believed to be the most difficult.
But now, S. Nolte and A. Szameit together with an international team were succeeded to characterize extensively the behavior of electrons in this material. In the current issue of the renowned journal "Nature Materials" (DOI: 10.1038/NMAT3783), the researchers present experimental data, allowing an accurately mimic of the electronic properties, particularly in the edge structures of graphene crystal. The nature of the edge regions is crucial for the overall electronic characteristics of the crystal.
For their experiments they used a photonic model of graphene. For that, the physicists laser-engraved several hundred tiny fibers into a glass chip, which are arranged like the graphene in a honeycomb pattern and thus simulates the single-layer crystal structure. Now, when light is irradiated into the model, the light particles (photons) spread over the entire crystal - like the extremely mobile electrons in real graphene cater for its tremendous electrical conductivity.

Like this, the researchers of the University of Jena, the San Francisco State University and the Technion - Israel Institute of Technology in Haifa could study the behavior of photons in the peripheral areas of the model crystal. Because of the basic hexagonal crystal structure of the graphene, the edges can take different forms. These edges form - like the fringe to a carpet - either a zigzag pattern, a "beard" or "armrest shape." Under certain experimental conditions, the electrons can move only along these edges and do not move into the interior of the crystal. But, whether such so-called "surface states" can develop, it is depended crucially upon the particular form of the edge structure. The existence of such states is important to control the conductivity of graphene.

In the current publication, for the first time ever researchers have verified the surface state of beard shaped edge structures. These were theoretically predicted, but could not be studied experimentally so far, because real graphene with beard shaped edges is too unstable. Based on the stable photonic model , there is no such problem anymore. The researcher also demonstrated a hitherto completely unknown surface condition. "This means that the previous theoretical description of the electron motion along the edges of the graphene crystal was incomplete and we could close this gap now," resumes Szameit. With the knowledge, it is now possible to open up new opportunities for graphene-based applications.

Plotnik Y. et al. Observation of Tamm-like edge states in 'photonic graphene', Nature Materials 2013, DOI:10.1038/nmat3783

Jun.-Prof. Dr. Alexander Szameit
Institut für Angewandte Physik der Friedrich-Schiller-Universität Jena
Albert-Einstein-Straße 15, 07745 Jena
Phone: 03641 / 947985

News from: 13.11.2013 12:40
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