Properties of Graphene: A Theoretical Perspective

In this review, we provide an in-depth description of the physics of monolayer and bilayer graphene from a theorist's perspective. We discuss the physical properties of graphene in an external magnetic field, reflecting the chiral nature of the quasiparticles near the Dirac point with a Landau level at zero energy. We address the unique integer quantum Hall effects, the role of electron correlations, and the recent observation of the fractional quantum Hall effect in the monolayer graphene. The quantum Hall effect in bilayer graphene is fundamentally different from that of a monolayer, reflecting the unique band structure of this system. The theory of transport in the absence of an external magnetic field is discussed in detail, along with the role of disorder studied in various theoretical models. We highlight the differences and similarities between monolayer and bilayer graphene, and focus on thermodynamic properties such as the compressibility, the plasmon spectra, the weak localization correction, quantum Hall effect, and optical properties. Confinement of electrons in graphene is nontrivial due to Klein tunneling. We review various theoretical and experimental studies of quantum confined structures made from graphene. The band structure of graphene nanoribbons and the role of the sublattice symmetry, edge geometry and the size of the nanoribbon on the electronic and magnetic properties are very active areas of research, and a detailed review of these topics is presented. Also, the effects of substrate interactions, adsorbed atoms, lattice defects and doping on the band structure of finite-sized graphene systems are discussed. We also include a brief description of graphane -- gapped material obtained from graphene by attaching hydrogen atoms to each carbon atom in the lattice.Comment: 189 pages. submitted in Advances in Physic

Ro-vibrational modes of H2 in 4H-SiC and 2H-GaN

We present the results of theoretical calculations of the structure, diffusion and rotational energies, and the ro-vibrational modes of the hydrogen molecule in the hexagonal part of 4H-SiC and in 2H-GaN. In both materials, the molecule is stable and aligned along the c-axis. Its rotational barrier is sufficiently large that ortho- and para-forms have almost degenerate ro-vibrational modes. The origin of two modes at 4090 and 4110 cm-1 attributed to molecules observed by multi-transmission FTIR experiments on Mg doped insulating GaN grown by OMVPE is discussed. \ua9 2003 Elsevier B.V. All rights reserved