Transport in graphene antidot barriers and tunneling devices

Periodic arrays of antidots, i.e. nanoscale perforations, in graphene enable tight confinement of carriers and efficient transport barriers. Such barriers evade the Klein tunneling mechanism by being of the mass rather than electrostatic type. While all graphene antidot lattices (GALs) may support directional barriers, we show, however, that a full transport gap exists only for certain orientations of the GAL. Moreover, we assess the applicability of gapped graphene and the Dirac continuum approach as simplified models of various antidot structures showing that, in particular, the former is an excellent approximation for transport in GALs supporting a bulk band gap. Finally, the transport properties of a GAL based resonant tunneling diode is analyzed indicating that such advanced graphene based devices may, indeed, be realized using GAL structures.Comment: 12 pages, 9 figures, accepted for publication on Journal of Applied Physic

Tight-binding study of the magneto-optical properties of gapped graphene

We study the optical properties of gapped graphene in presence of a magnetic field. We consider a model based on the Dirac equation, with a gap introduced via a mass term, for which analytical expressions for the diagonal and Hall optical conductivities can be derived. We discuss the effect of the mass term on electron-hole symmetry and $\pi$-$\pi^*$ symmetry and its implications for the optical Hall conductivity. We compare these results with those obtained using a tight-binding model, in which the mass is modeled via a staggered potential and a magnetic field is included via a Peierls substitution. Considering antidot lattices as the source of the mass term, we focus on the limit where the mass term dominates the cyclotron energy. We find that a large gap quenches the effect of the magnetic field. The role of overlap between neighboring $\pi$ orbitals is investigated, and we find that the overlap has pronounced consequences for the optical Hall conductivity that are missed in the Dirac model.Comment: 10 pages, 9 figures, submitted for Physical Review