Nonlinear optical response in gapped graphene

Optical response and excitons in gapped graphene

Coherent nonlinear optical response of graphene.

We investigate the nonlinear optical properties of graphene flakes using four-wave mixing. The corresponding third-order optical susceptibility is found to be remarkably large and only weakly dependent on the wavelength in the near-infrared frequency range. The magnitude of the response is in good agreement with our calculations based on the nonlinear quantum response theory.

Inhomogeneity and nonlinear screening in gapped bilayer graphene

We demonstrate that for gapped bilayer graphene, the nonlinear nature of the screening of an external disorder potential and the resulting inhomogeneity of the electron liquid are crucial for describing the electronic compressibility. In particular, traditional diagrammatic methods of many-body theory do not include this inhomogeneity and therefore fail to reproduce experimental data accurately...

Supercritical Coulomb Impurities in Gapped Graphene

We study the problem of Coulomb field-induced charging of the ground state in a system of 2D massive Dirac particles – gapped graphene. As in its 3D QED counterpart, the critical Coulomb coupling is renormalized to higher values, compared to the massless case. We find that in gapped graphene a novel supercritical regime is possible, where the screening charge is comparable to the impurity charg...

Thermally activated conductivity in gapped bilayer graphene

This is a theoretical study of electron transport in gated bilayer graphene — a novel semiconducting material with a tunable band gap. It is shown that the quantum mechanical superposition between conduction and valence band states enhances the subgap conductivity and facilitates the thermally activated transport. The mechanism proposed can also lead to the non-monotonic conductivity vs. temper...