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Metal-intercalated graphene on Ir(111) exhibits phonon signatures in inelastic elec- tron tunneling spectroscopy with strengths that depend on the intercalant. Extraor- dinarily strong graphene phonon signals are observed for Cs intercalation. Li interca- lation likewise induces clearly discriminable phonon signatures, albeit less pronounced than observed for Cs. The signal can be finely tuned by the alkali metal coverage and gradually disappears upon increasing the junction conductance from tunneling to con- tact ranges. In contrast to Cs and Li, for Ni-intercalated graphene the phonon signals stay below the detection limit in all transport ranges. Going beyond the conventional two-terminal approach, transport calculations provide a comprehensive understanding of the subtle interplay between the graphene{electrode coupling and the observation of graphene phonon spectroscopic signatures.

The complex electronic properties of $\mathrm{ZrTe_5}$ have recently stimulated in-depth investigations that assigned this material to either a topological insulator or a 3D Dirac semimetal phase. Here we report a comprehensive experimental and theoretical study of both electronic and structural properties of $\mathrm{ZrTe_5}$, revealing that the bulk material is a strong topological insulator (STI). By means of angle-resolved photoelectron spectroscopy, we identify at the top of the valence band both a surface and a bulk state. The dispersion of these bands is well captured by ab initio calculations for the STI case, for the specific interlayer distance measured in our x-ray diffraction study. Furthermore, these findings are supported by scanning tunneling spectroscopy revealing the metallic character of the sample surface, thus confirming the strong topological nature of $\mathrm{ZrTe_5}$., Comment: 5 pages, 4 figures

We report the structural and electronic properties of an artificial graphene/Ni(111) system obtained by the intercalation of a monoatomic layer of Ni in graphene/Ir(111). Upon intercalation, Ni grows epitaxially on Ir(111), resulting in a lattice mismatched graphene/Ni system. By performing Scanning Tunneling Microscopy (STM) measurements and Density Functional Theory (DFT) calculations, we show that the intercalated Ni layer leads to a pronounced buckling of the graphene film. At the same time an enhanced interaction is measured by Angle-Resolved Photo-Emission Spectroscopy (ARPES), showing a clear transition from a nearly-undisturbed to a strongly-hybridized graphene $\pi$-band. A comparison of the intercalation-like graphene system with flat graphene on bulk Ni(111), and mildly corrugated graphene on Ir(111), allows to disentangle the two key properties which lead to the observed increased interaction, namely lattice matching and electronic interaction. Although the latter determines the strength of the hybridization, we find an important influence of the local carbon configuration resulting from the lattice mismatch., Comment: 9 pages, 3 figures, Accepted for publication in Phys. Rev. B

Realization of graphene moir\'e superstructures on the surface of 4d and 5d transition metals offers templates with periodically modulated electron density, which is responsible for a number of fascinating effects, including the formation of quantum dots and the site selective adsorption of organic molecules or metal clusters on graphene. Here, applying the combination of scanning probe microscopy/spectroscopy and the density functional theory calculations, we gain a profound insight into the electronic and topographic contributions to the imaging contrast of the epitaxial graphene/Ir(111) system. We show directly that in STM imaging the electronic contribution is prevailing compared to the topographic one. In the force microscopy and spectroscopy experiments we observe a variation of the interaction strength between the tip and high-symmetry places within the graphene moir\'e supercell, which determine the adsorption cites for molecules or metal clusters on graphene/Ir(111)., Comment: submitted on Sep, 6th 2012

The electronic and crystallographic structure of the graphene/Rh(111) moir\'e lattice is studied via combination of density-functional theory calculations and scanning tunneling and atomic force microscopy (STM and AFM). Whereas the principal contrast between hills and valleys observed in STM does not depend on the sign of applied bias voltage, the contrast in atomically resolved AFM images strongly depends on the frequency shift of the oscillating AFM tip. The obtained results demonstrate the perspectives of application atomic force microscopy/spectroscopy for the probing of the chemical contrast at the surface., Comment: manuscript and supplementary information; submitted to Appl. Phys. Lett. on 01.03.2011

The Fe$_3$O$_4$(111)/graphene/Ni(111) trilayer is proposed to be used as an ideal spin-filtering sandwich where the half-metallic properties of magnetite are used. Thin magnetite layers on graphene/Ni(111) were prepared via successive oxidation of thin iron layer predeposited on graphene/Ni(111) and formed system was investigated by means of low-energy electron diffraction (LEED) and photoelectron spectroscopy (PES) of core levels as well as valence band. The electronic structure and structural quality of the graphene film sandwiched between two ferromagnetic layers remains unchanged upon magnetite formation as confirmed by LEED and PES data., Comment: 13 pages, 4 figures

Topographic scanning tunneling microscopy (STM) images of epitaxial single layer graphene on the Rh(111) surface reveal that extended single crystalline graphene domains are produced without any defects on a large scale. High resolution imaging shows that the moir\'e structure resulting from the lattice mismatch between the Rh(111) substrate and graphene is highly corrugated, containing regions of an additional spatial modulation in the moir\'e supercell compared with those previously reported for graphene on Ir(111) or graphene on Ru(0001). These areas, which correspond to the "bridge" regions of the moir\'e structure appear as depressions in STM images indicating a strong orbital hybridization between the graphene layer and the metallic substrate. Valence-band photoemission confirms the strong hybridization between graphene and Rh(111) which leads to the pronounced corrugation of the graphene layer. Our findings underline the importance of considering substrate effects in epitaxially grown graphene layers for the design of graphene-based nanoscale systems., Comment: Submitted to Nano Lett. on May, 17th 2010

The article presents the work on the investigation of the surface structure as well as electronic and magnetic properties of graphene layer on a lattice matched surface of a ferromagnetic material, Ni(111)., Comment: accepted in New J. Phys

We report an element-specific investigation of electronic and magnetic properties of the graphene/Ni(111) system. Using magnetic circular dichroism, the occurrence of an induced magnetic moment of the carbon atoms in the graphene layer aligned parallel to the Ni 3d magnetization is observed. We attribute this magnetic moment to the strong hybridization between C $\pi$ and Ni 3d valence band states. The net magnetic moment of carbon in the graphene layer is estimated to be in the range of $0.05-0.1 \mu_B$ per atom., Comment: 10 pages, 3 figures

Here we report spin- and angle-resolved photoemission studies of the inert graphene layer formed on the surface of a ferromagnetic material, Ni(111). X-ray photoemission and spin-resolved spectroscopy of secondary electrons reveal that graphene behaves like a protection layer on the Ni(111) surface preventing its reaction with adsorbed oxygen. Angle-resolved photoelectron spectroscopy of $\pi$ states of graphene on Ni(111) shows a strong dependence of binding energy of these states on the direction of magnetization of the sample. We conclude that the observed extraordinary high "splitting" up to 225 meV of the $\pi$ band in the graphene layer is a manifes-tation of the Rashba effect which provides a direct possibility to a flexible control of an electron spin in a graphene-based spin-FET., Comment: 3 pages, 3 figures

Angle-resolved photoemission spectra of a monolayer of Yb on W(110) reveal energy splittings and dispersion of the Yb 4f states that are obviously due to their hybridization with W-derived valence bands. These effects occur at well defined points of the surface Brillouin zone although a smearing over reciprocal space is expected from the structural incoherence of the Yb and W lattices. We conclude therefore that dispersion is not related to the periodic arrangement of the $4f$ states but reflects the k-dependent interaction of a single Yb 4f impurity with W bands., Comment: 7 pages, 4 figures

Here we report the photoemission studies of intercalation process of Fe underneath graphene layer on Ni(111). The process of intercalation was monitored via XPS of corresponding core levels and UPS of the graphene-derived $\pi$ states in the valence band. \textit{fcc}-Fe films with thickness of 2-5 monolayers at the interface between graphene and Ni(111) form epitaxial magnetic layer passivated from the reactive environment, like for example oxygen gas., Comment: 8 pages, 3 figures

Here, we report on angle-resolved photoemission studies of the electronic $\pi$ states of high-quality epitaxial graphene layer on a Ni(111) surface. In this system electron binding energy of the $\pi$ states shows a strong dependence on the magnetization reversal of the Ni film. The observed extraordinary large energy shift up to 225 meV of the graphene-derived $\pi$-band peak position for opposite magnetization directions is attributed to a manifestation of the Rashba interaction of spin-polarized electrons in the $\pi$ band with the large effective electric field at graphene/Ni interface. Our findings show that an electron spin in the graphene layer can be manipulated in a controlled way and have important implications for graphene-based spintronic devices., Comment: 12 pages, 3 figures in JPEG-format

Spin- and angle-resolved resonant (Ce $4d\to4f$) photoemission spectra of a monolayer Ce on Fe(110) reveal spin-dependent changes of the Fermi-level peak intensities. That indicate a spin-dependence of $4f$ hybridization and, thus, of $4f$ occupancy and local moment. The phenomenon is described in the framework of the periodic Anderson model by $4f$ electron hopping into the exchange split Fe 3d derived bands that form a spin-gap at the Fermi energy around the $\bar{\Gamma}$ point of the surface Brillouin zone.

Electronic and structural properties of ultrathin MgO layers grown on epitaxial Fe(110) films were investigated at room temperature by means of spin-resolved photoelectron spectroscopy, Auger-electron spectroscopy, and low energy electron diffraction. The spin polarization at the Fermi level of the Fe(110) film decreases abruptly with increasing thickness of MgO layer up to 7 \AA. This behavior is attributed to the formation of a thin FeO layer at the MgO(111)/Fe(110) interface, attenuating the intrinsic spin polarization., Comment: 11 pages, 4 figures