Impurity scattering and Friedel oscillations in mono-layer black phosphorus

We study the effect of impurity scattering effect in black phosphorurene (BP) in this work. For single impurity, we calculate impurity induced local density of states (LDOS) in momentum space numerically based on tight-binding Hamiltonian. In real space, we calculate LDOS and Friedel oscillation analytically. LDOS shows strong anisotropy in BP. Many impurities in BP are investigated using $T$-matrix approximation when the density is low. Midgap states appear in band gap with peaks in DOS. The peaks of midgap states are dependent on impurity potential. For finite positive potential, the impurity tends to bind negative charge carriers and vise versa. The infinite impurity potential problem is related to chiral symmetry in BP

Evidence for spin-flip scattering and local moments in dilute fluorinated graphene

The issue of whether local magnetic moments can be formed by introducing adatoms into graphene is of intense research interest because it opens the window to fundamental studies of magnetism in graphene, as well as of its potential spintronics applications. To investigate this question we measure, by exploiting the well-established weak localization physics, the phase coherence length L_phi in dilute fluorinated graphene. L_phi reveals an unusual saturation below ~ 10 K, which cannot be explained by non-magnetic origins. The corresponding phase breaking rate increases with decreasing carrier density and increases with increasing fluorine density. These results provide strong evidence for spin-flip scattering and points to the existence of adatom-induced local magnetic moment in fluorinated graphene. Our results will stimulate further investigations of magnetism and spintronics applications in adatom-engineered graphene.Comment: 9 pages, 4 figures, and supplementary materials; Phys. Rev. Lett. in pres

Effective mass of electrons and holes in bilayer graphene: Electron-hole asymmetry and electron-electron interaction

Precision measurements of the effective mass m* in high-quality bilayer graphene using the temperature dependence of the Shubnikov–de Haas oscillations are reported. In the density range 0.7 × 1012 \u3c n \u3c 4.1 × 1012 cm−2, both the hole mass m*h and the electron mass m*e increase with increasing density, demonstrating the hyperbolic nature of the bands. The hole mass m*h is approximately 20–30% larger than the electron mass m*e . Tight-binding calculations provide a good description of the electron-hole asymmetry and yield an accurate measure of the interlayer hopping parameter v4 = 0.063. Both m*h and m*e are suppressed compared with single particle values, suggesting renormalization of the band structure of bilayer graphene induced by electron-electron interaction

The quantum scattering time and its implications on scattering sources in graphene (Supplementary)

Supplementary Information Content: 1. Sample preparation; 2. Background subtraction of Shubnikov-de Haas (SdH) oscillations; 3. The effect of density inhomogeneity on the quantum scattering time tau_q; 4. Determine the concentration of charged impurity n_imp at a distance z; 5. Scattering from charges in the bulk of the SiO_2 substrate.Comment: Supplementary materials to arXiv:0909.1595. 5 pages, 5 figure

Effective mass of electrons and holes in bilayer graphene: Electron-hole asymmetry and electron-electron interaction

Precision measurements of the effective mass m* in high-quality bilayer graphene using the temperature dependence of the Shubnikov–de Haas oscillations are reported. In the density range 0.7 × 1012 \u3c n \u3c 4.1 × 1012 cm−2, both the hole mass m*h and the electron mass m*e increase with increasing density, demonstrating the hyperbolic nature of the bands. The hole mass m*h is approximately 20–30% larger than the electron mass m*e . Tight-binding calculations provide a good description of the electron-hole asymmetry and yield an accurate measure of the interlayer hopping parameter v4 = 0.063. Both m*h and m*e are suppressed compared with single particle values, suggesting renormalization of the band structure of bilayer graphene induced by electron-electron interaction

High-Mobility Few-Layer Graphene Field Effect Transistors Fabricated on Epitaxial Ferroelectric Gate Oxides

The carrier mobility \mu of few-layer graphene (FLG) field-effect transistors increases ten-fold when the SiO_2 substrate is replaced by single-crystal epitaxial Pb(Zr_0.2Ti_0.8)O_3 (PZT). In the electron-only regime of the FLG, \mu reaches 7x10^4 cm^2/Vs at 300K for n = 2.4x10^12/cm^2, 70% of the intrinsic limit set by longitudinal acoustic (LA) phonons; it increases to 1.4x10^5 cm^2/Vs at low temperature. The temperature-dependent resistivity \rho(T) reveals a clear signature of LA phonon scattering, yielding a deformation potential D = 7.8+/-0.5 eV.Comment: 5 pages, 4 figure

Spin correlated interferometry for polarized and unpolarized photons on a beam splitter

Spin interferometry of the 4th order for independent polarized as well as unpolarized photons arriving simultaneously at a beam splitter and exhibiting spin correlation while leaving it, is formulated and discussed in the quantum approach. Beam splitter is recognized as a source of genuine singlet photon states. Also, typical nonclassical beating between photons taking part in the interference of the 4th order is given a polarization dependent explanation.Comment: RevTeX, 19 pages, 1 ps figure, author web page at http://m3k.grad.hr/pavici

Deposition of High-Quality HfO2 on Graphene and the Effect of Remote Oxide Phonon Scattering

We demonstrate atomic layer deposition of high-quality dielectric HfO2 films on graphene and determine the magnitude of remote oxide surface phonon scattering in dual-oxide structures. The carrier mobility in these HfO2-covered graphene samples reaches 20 000 cm2/Vs at low temperature. Distinct contributions to the resistivity from surface optical phonons in the SiO2 substrate and the HfO2 overlayer are isolated. At 300 K, surface phonon modes of the HfO2 film centered at 54 meV limit the mobility to approximately 20 000 cm2/Vs