P. Le Fèvre

First Direct Observation of a Nearly Ideal Graphene Band Structure

Angle-resolved photoemission and x-ray diffraction experiments show that multilayer epitaxial graphene grown on the SiC(0001) surface is a new form of carbon that is composed of effectively isolated graphene sheets. The unique rotational stacking of these films causes adjacent graphene layers to electronically decouple leading to a set of nearly independent linearly dispersing bands (Dirac cones) at the graphene K point. Each cone corresponds to an individual macroscale graphene sheet in a multilayer stack where AB-stacked sheets can be considered as low density faults.

A wide-bandgap metal-semiconductor-metal nanostructure made entirely from graphene

The electronic properties of graphene are spatially controlled from metallic to semiconducting by patterning steps into the underlying silicon carbide substrate. This bottom-up approach could be the basis for integrated graphene electronics.

Spin to Charge Conversion at Room Temperature by Spin Pumping into a New Type of Topological Insulator: α -Sn Films

We present results on spin to charge current conversion in experiments of resonant spin pumping into the Dirac cone with helical spin polarization of the elemental topological insulator (TI) α-Sn. By angle-resolved photoelectron spectroscopy (ARPES), we first check that the Dirac cone (DC) at the α-Sn (0 0 1) surface subsists after covering Sn with Ag. Then we show that resonant spin pumping at room temperature from Fe through Ag into α-Sn layers induces a lateral charge current that can be ascribed to the inverse Edelstein effect by the DC states. Our observation of an inverse Edelstein effect length much longer than those generally found for Rashba interfaces demonstrates the potential of TIs for the conversion between spin and charge in spintronic devices. By comparing our results with data on the relaxation time of TI free surface states from time-resolved ARPES, we can anticipate the ultimate potential of the TI for spin to charge conversion and the conditions to reach it.1 Unité Mixte de Physique CNRS/Thales, 91767 Palaiseau, France 2 Université Paris-Sud, Université Paris-Saclay, UMR137, 91767 Palaiseau, France 3 Université Grenoble Alpes, INAC-SP2M, F-38000 Grenoble, France 4 CEA, Institut Nanosciences et Cryogénie, F-38000 Grenoble, France 5 Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan 6 Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan 7 UR1 CNRS, Synchrotron SOLEIL, Saint-Aubin, 91192 Gif sur Yvette, France 8 Synchrotron SOLEIL, Saint-Aubin, 91192 Gif sur Yvette, France

Symmetry breaking in commensurate graphene rotational stacking: Comparison of theory and experiment

Graphene stacked in a Bernal configuration (

Crystallographic structure of cobalt films on Cu(001): elastic deformation to a tetragonal structure

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Nesting between hole and electron pockets in Ba ( Fe 1 − x Co x ) 2 As 2 ( x = 0 – 0.3 ) observed with angle-resolved photoemission

relative rotations between sheets) differs electronically from isolated graphene due to the broken symmetry introduced by interlayer bonds forming between only one of the two graphene unit cell atoms. A variety of experiments have shown that non-Bernal rotations restore this broken symmetry; consequently, these stacking varieties have been the subject of intensive theoretical interest. Most theories predict substantial changes in the band structure ranging from the development of a Van Hove singularity and an angle-dependent electron localization that causes the Fermi velocity to go to zero as the relative rotation angle between sheets goes to zero. In this work we show by direct measurement that non-Bernal rotations preserve the graphene symmetry with only a small perturbation due to weak effective interlayer coupling. We detect neither a Van Hove singularity nor any significant change in the Fermi velocity. These results suggest significant problems in our current theoretical understanding of the origins of the band structure of this material.

Significant reduction of electronic correlations upon isovalent Ru substitution of BaFe2As2.

Abstract The stable structure of cobalt is hexagonal closed-packed (hcp), but cobalt can be stabilized in a distorted face-centered cubic structure (fcc) by epitaxy on Cu(001). The deviation from the isotropic fcc structure is determined by surface-extended X-ray absorption fine structure (EXAFS). A polarization dependent first shell analysis of the EXAFS spectra shows that the Co/Cu(001) films have a face-centered tetragonal structure (fct): the mean nearest-neighbour distance parallel to the surface is 2.55A(same value as in bulk copper) and the interlayer bond length is 2.50A: the films are in perfect epitaxy on copper (001) with a contraction of the lattice parameter perpendicular to the surface of 4%, in agreement with the continuum elasticity theory. A constant tetragonalization is observed for films of 2 to 15 monolayers. A simulation of the EXAFS spectra is also done using the FEFF code. In order to simulate the polarization dependence of the experimental spectra, we have introduced in this theoretical calculation a polarization dependence of the paths (single scattering and multiple scattering ones) based on a plane wave approximation. This simple model gives a good agreement between calculated and experimental polarization dependent EXAFS spectra both on bulk hcp cobalt and on the face-centered tetragonal films Co/Cu(001); this agreement confirms the structure determined from the first shell analysis.

Influence of the substrate oxidation state in the growth of copper clusters on Al2O3(0001) surface: a XANES and EXAFS study

We present a comprehensive angle-resolved photoemission study of the three-dimensional electronic structure of

A surface EXAFS study of thin nickel deposits on (110) TiO2 surfaces

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Large Temperature Dependence of the Number of Carriers in Co-Doped BaFe 2 As 2

. The wide range of dopings covered by this study,