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NEOCLASSICAL THEORY OF INTERACTION 95

ring resonators gives the material a negative magnetic permeability, whereas the array of
vertical wires gives it a negative permittivity in microwave frequency range.
Note in conclusion that the era of SNG and DNG metamaterials practically started in 1996 and
1999 when British scientist John B. Pendry published his new conception of artificially
produced SNR materials. In 2000, a research group from the University of California at San
Diego (UCSD) fabricated and tested the first DRG metamaterial. They combined two structures
proposed by J. Pendry: the lattice consisting of metal inclusions in the form of conducting
cylinders (vertical lines) and split-rings similar to shown in Figure 2.8.10. A significant number
of the following theoretical and experimental data confirmed the existence of metamaterials
predicted by Veselago.

Figure 2.8.10 DNG material structure

2.9 GRAPHENE

2.9.1 Introduction
We decided to devote the last section of this chapter to relatively new but very fascinating
material named graphene - a single layer of bulk graphite and a 2D electronic material. The
name of graphene came as the combination of “Graph” (shortened from graphite) and suffix “-
ene” and was introduced by German chemist H. P. Boehm in 1962. The graphene is a natural
one-atom-thick crystal consisting of a single sheet of carbon
atoms (black balls) in truly two-dimensional (2D) honeycomb
lattice as Figure 2.9.1 demonstrates. The strong bonds between
the carbon atoms (black spheres) are shown in the form of yellow
rods. Each carbon atom has a total of 6 electrons; 2 in the inner
shell and 4 in the outer shell. Three of these valence electrons
participate in sp bonds to their next neighbor atoms in the form
2
of sigma bonds, while the fourth occupies an orbital that is
Figure 2.9.1 Idealized oriented perpendicular to the sheet constituting the so-called pi(π)
graphene sheet bonds. Such electrons are delocalized, highly-mobile and move
structure
incredibly fast above and below the graphene lattice.

Two British scientists Andre Gaim and Konstantin Novoselov at the University of Manchester
discovered graphene in 2004 and received the 2010 Nobel Prize in Physics for their