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...

It has been predicted that application of a strong electric field perpendicular to the plane of bilayer graphene can induce a significant band gap. We have measured the optical conductivity of bilayer graphene with an efficient electrolyte top gate for a photon energy range of 0.2-0.7 eV. We see the emergence of new transitions as a band gap opens. A band gap approaching 200 meV is observed whe...

The resistance of dual-gated bilayer graphene is measured as a function of temperature and gating electric fields in the Corbino geometry which precludes edge transport. The temperature-dependent resistance is quantitatively described by a two-channel conductance model including parallel thermal activation and variable range hopping channels, which gives the electric-field-dependent band gap wh...

The optical conductivities of graphene layers are strongly dependent on their stacking orders. Our first-principle calculations show that, while the optical conductivities of single-layer graphene (SLG) and bilayer graphene (BLG) with Bernal stacking are almost frequency-independent in the visible region, the optical conductivity of twisted bilayer graphene (TBG) is frequency-dependent, giving ...

We calculate the electronic band structure of ABA-stacked trilayer graphene in the presence of external gates, using a self-consistent Hartree approximation to take account of screening. In the absence of a gate potential, there are separate pairs of linear and parabolic bands at low energy. A gate field perpendicular to the layers breaks mirror reflection symmetry with respect to the central l...

A. F. Young,1 C. R. Dean,2,3 I. Meric,2 S. Sorgenfrei,2 H. Ren,1 K. Watanabe,4 T. Taniguchi,4 J. Hone,3 K. L. Shepard,2 and P. Kim1 1Department of Physics, Columbia University, New York, New York 10027, USA 2Department of Electrical Engineering, Columbia University, New York, New York 10027, USA 3Department of Mechanical Engineering, Columbia University, New York, New York 10027, USA 4Advanced ...

Opening, in a controllable way, energy gap in graphene electron spectrum is necessary for many potential applications, including an efficient carbon-based transistor. We have shown that this can be reached by a chemical functionalization of bilayer graphene. Using various dopants, such as H, F, Cl, Br, OH, CN, CCH, NH2, COOH, and CH3 one can vary the gap value smoothly between 0.64 and 3 eV and...

We use graphene bubbles to study the Raman spectrum of graphene under biaxial (e.g., isotropic) strain. Our Gruneisen parameters are in excellent agreement with the theoretical values. Discrepancy in the previously reported values is attributed to the interaction of graphene with the substrate. Bilayer balloons (intentionally pressurized membranes) have been used to avoid the effect of the subs...

Calculations based on the first-principles pseudopotential plane-wave method and density-functional theory are performed to investigate the electronic properties of graphene, bilayer graphene, multilayer graphene, and graphite. From an analysis of the electronic band structure close to the Fermi level, we have quantified the gradual change in the Fermi surface topology from the point-like struc...

We study, within the tight-binding approximation, the electronic properties of a graphene bilayer in the presence of an external electric field applied perpendicular to the system-a biased bilayer. The effect of the perpendicular electric field is included through a parallel plate capacitor model, with screening correction at the Hartree level. The full tight-binding description is compared wit...