Graphene With Electronic Stripes

Graphene stripes (alphagalileo.org)

Graphene is known as semi-metallic properties, a zero-gap semiconductors. Graphene has a honeycomb-like shape, hexagonal, a 2D sheet of carbon atoms are sp2-bonds. At low energies, at the corner of the hexagonal Brillouin zone, the electron and hole have an effective mass equal to zero. Thus, graphene is often portrayed through the theory of special relativity and the Dirac equation. That fact has continued since 1947.

Researchers from the London Centre for Nanotechnology (LCN) have discovered electronic stripes, called ‘charge density waves’, on the surface of the graphene sheets that make up a graphitic superconductor. This is the first time these stripes have been seen on graphene, and the finding is likely to have profound implications for the exploitation of this recently discovered material, which scientists believe will play a key role in the future of nanotechnology. The discovery is reported in Nature Communications, 29th November. Graphene is found in the marks made ​​by pencil graphite. The physical properties and remarkable electronic on graphene, a material widely used for high-level technology. Such as transparent electrodes for flat screen TV, with the fast energy-efficient transistors, and the ultra-strong composite materials. The scientists are now devoting major efforts to understand and control the properties of these materials.

The LCN team donated extra electrons to a graphene surface by sliding calcium metal atoms underneath it. One would normally expect these additional electrons to spread out evenly on the graphene surface, just as oil spreads out on water. But by using an instrument known as a scanning tunneling microscope, which can image individual atoms, the researchers have found that the extra electrons arrange themselves spontaneously into nanometer-scale stripes. This unexpected behavior demonstrates that the electrons can have a life of their own which is not connected directly to the underlying atoms. The results inspire many new directions for both science and technology. For example, they suggest a new method for manipulating and encoding information, where binary zeros and ones correspond to stripes running from north to south and running from east to west respectively.

Experiments by the LCN team, they use the chemical composition CaC6. The stripes correspond to a charge density wave with a period three times that of the Ca superlattice. Although the positions of the Ca intercalants are modulated, no displacements of the carbon lattice are detected, indicating that the graphene sheets host the ideal charge density wave. This provides an exceptionally simple material—graphene—as a starting point for understanding the relation between stripes and superconductivity.

Source: http://www.alphagalileo.org/ViewItem.aspx?ItemId=114944&CultureCode=en