Published: 13 December 2012, 10:13
Together with colleagues from the Technion-Israel Institute of Technology in Haifa, the ACP scientists Tünnermann, Nolte and Szameit have published an original research article in Nature Photonics, for the first time accessing and demonstrating the pseudo-magnetic properties of graphene in an equivalent discrete photonic lattice. Graphene is the first realized two-dimensional material, a single layer of carbon atoms arranged in a honeycomb pattern. In many ways it is very different from three-dimensional solids. Amongst other things, its electrons are extremely mobile which gives the material a huge electrical conductivity.
"Due to its unique properties the material is a promising future material ", resumes Prof. Dr. Alexander Szameit. However, to be able to use the material for special applications, in a first step scientists have to understand the fundamental properties of graphene much better. With their actual work, the ACP scientists made an important contribution. In the current issue of the renowned journal "Nature Photonics" they present a photonic model system which allows studying certain physical properties of graphene in much more detail as in the real material. The focus laid on the effect of so-called pseudo-magnetic fields which can be applied to graphene by a special mechanical strain. Thus, the interaction between magnetic fields and graphene can be investigated without generating a real magnetic field and advantageously the reached field strengths are much stronger than those of real magnets.
In practice, few hundred tiny waveguides were written into a glass chip by a laser, arranged in a honeycomb pattern as the atoms in graphene. "This system enables us to simulate the mono-layer atomic structure of graphene in a photonic model" says Julia Zeuner, a PhD-student in Szameit's team. After launching light into a single waveguide the light spreads with light speed across the photonic graphene structure - in the same way as the extremely mobile electrons in the real graphene cause its extreme electrical conductivity. "Also in this graphene model the interaction with simulated magnetic fields can be investigated", says Jun.-Prof. Szameit. However, this cannot be achieved by mechanical strain, but the "deformation" of the honeycomb pattern is written with the laser directly into the glass chip. The stronger the lattice is strained, the higher the "field strength" of the simulated magnetic effect is. If light is launched into the graphene model system under the influence of such a pseudo-magnetic field, it was observed that the "conductivity" decreased significantly with increasing field strength. At pseudo-magnetic field strength of unimaginable 7000 Tesla - the most powerful modern MRI scanners reach field strengths of about 3 Tesla - the conductivity of the graphene model approaches zero. With their work, the ACP physicists opened an entirely new field of research being able to manipulate light by the help of ultra-strong virtual magnetic fields.
Rechtsmann et al., "Strain-induced pseudomagnetic field and photonic Landau levels in dielectric structures," Nature Photonics, doi:10.1038/nphoton.2012.302 (2012).
Jun.-Prof. Dr. Alexander Szameit
Phone: 03641 / 947985