Biased bilayer graphene: semiconductor with a gap tunable by the electric field effect

We demonstrate that the electronic gap of a graphene bilayer can be controlled externally by applying a gate bias. From the magnetotransport data (Shubnikov-de Haas measurements of the cyclotron mass), and using a tight-binding model, we extract the value of the gap as a function of the electronic density. We show that the gap can be changed from zero to midinfrared energies by using fields of less, approximately < 1 V/nm, below the electric breakdown of SiO2. The opening of a gap is clearly seen in the quantum Hall regime.     

Graphene: materials in the Flatland (Nobel lecture)

Much like the world described in Abbott's "Flatland", graphene is a two-dimensional object. And, as "Flatland" is "A Romance of Many Dimensions", graphene is much more than just a flat crystal. It possesses a number of unusual properties which are often unique or superior to those in other materials. In this brief lecture I would like to explain the reason for my (and many other people's) fascination with this material, and invite the reader to share some of the excitement I've experienced while researching it.     

Properties of Solutions and Films of Fibroin-Poly-3-Hydroxybutyrate Polymer Blends

Solutions of fibroin-poly-3-hydroxybutyrate polymer blends in hexafluoro-2-propanol and films obtained after removal of the solvent are experimentally studied at various polymer ratios.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 1, 2005, pp. 155–160.Original Russian Text Copyright © 2005 by Sashina, Novoselov, Heinemann.     

Spin squeezing and quantum correlations

We discuss the notion of spin squeezing considering two mutually exclusive classes of spin-s states, namely, oriented and non-oriented states. Our analysis shows that the oriented states are not squeezed while non-oriented states exhibit squeezing. We also present a new scheme for construction of spin-s states using 2s spinors oriented along different axes. Taking the case of s=1, we show that the ‘non-oriented’ nature and hence squeezing arise from the intrinsic quantum correlations that exist among the spinors in the coupled state.     

Quantum Hall activation gaps in bilayer graphene

We have measured the quantum Hall activation gaps in bilayer graphene at filling factors $\nu =\pm 4$ and $\nu =\pm 8$ in high magnetic fields up to 30 T. We find that energy levels can be described by a 4-band relativistic hyperbolic dispersion. The Landau level width is found to contain a field independent background due to an intrinsic level broadening and a component which increases linearly with magnetic field.     

Complex Phosphates in the Li(Na)3]PO4-InPO4 Systems

Subsolidus sections in the systems Li₃PO₄-InPO₄ (950°C) and Na₃PO₄-InPO₄ (800, 900, and 1000°C) have been studied by X-ray powder diffraction. The compound Li₃In(PO₄)₂ has been synthesized, and the nasicon-type solid solution Li_{3(1 ? x)}In_{2 + x}(PO₄)₃ (0.67 ≤ x ≤ 0.80). has been found to exist. In the system Na₃PO₄-InPO₄, the solid solution Na_{3(1 ? x)}In_x/3PO₄ (0 ≤ x ≤ 0.2) and two complex phosphates exist: Na₃In(PO₄)₂ and Na₃In₂(PO₄)₃. These complex phosphates are dimorphic, with the irreversible-transition temperature equal to 675 and 820°C, respectively. Na₃In(PO₄)₂ degrades at 920°C. Ionic conductivity has been measured in some phases in the system.     

Selective spectroscopy of tunneling transitions between the Landau levels in vertical double-gate graphene–boron nitride–graphene heterostructures

The spectral and total electron densities of states in two-dimensional FeAs clusters, which simulate iron-based superconductors, have been calculated using the generalized quantum Monte Carlo algorithm within the full two-orbital model. Spectra have been reconstructed by solving the integral equation relating the Matsubara Green’s function and spectral density by the method combining the gradient descent and Monte Carlo algorithms. The calculations have been performed for clusters with dimensions up to 10 × 10 FeAs cells. The profiles of the Fermi surface for the entire Brillouin zone have been presented in the quasiparticle approximation. Data for the total density of states near the Fermi level have been obtained. The effect of the interaction parameter, size of the cluster, and temperature on the spectrum of excitations has been studied.