Giant effective charges and piezoelectricity in gapped graphene

Optical response and excitons in gapped graphene

Giant piezoelectricity on Si for hyperactive MEMS.

Microelectromechanical systems (MEMS) incorporating active piezoelectric layers offer integrated actuation, sensing, and transduction. The broad implementation of such active MEMS has long been constrained by the inability to integrate materials with giant piezoelectric response, such as Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PMN-PT). We synthesized high-quality PMN-PT epitaxial thin films on vicinal...

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...

Dynamical current-current susceptibility of gapped graphene

We present analytical expressions for the current-current correlation function in graphene for arbitrary frequency, wavevector, doping, and band gap induced by a mass term. In the static limit we analyze the Landau (orbital) and Pauli magnetization, as well as the Lindhard correction which describes Friedel and RKKY oscillations. In the nonrelativistic limit we compare our results with the situ...