A5013374721- Surface and Thin Film Phenomena
- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Magnetic properties of thin films
- Surface Chemistry and Catalysis
- Advanced Chemical Physics Studies
- Advanced Condensed Matter Physics
- Graphene research and applications
- Topological Materials and Phenomena
- Magnetic and transport properties of perovskites and related materials
- Molecular Junctions and Nanostructures
- Magnetism in coordination complexes
- Theoretical and Computational Physics
- Electronic and Structural Properties of Oxides
- 2D Materials and Applications
- Organic and Molecular Conductors Research
- Chemical and Physical Properties of Materials
- Semiconductor materials and interfaces
- Advanced Materials Characterization Techniques
- Electron and X-Ray Spectroscopy Techniques
- Heusler alloys: electronic and magnetic properties
- Copper-based nanomaterials and applications
- Transition Metal Oxide Nanomaterials
- Superconductivity in MgB2 and Alloys
- Machine Learning in Materials Science
Université de Lorraine
2015-2025
Centre National de la Recherche Scientifique
2015-2025
Institut Jean Lamour
2014-2025
Artistic Realization Technologies
2018
Délégation Centre-Est
2015-2017
Groupe de Physique des Matériaux
2003-2007
Laboratoire de Chimie Physique et Microbiologie pour l'Environnement
2003-2006
Laboratoire National des Champs Magnétiques Intenses
1996-2000
University of Stuttgart
2000
High Magnetic Field Laboratory
1997-1998
A joint experimental and theoretical study is presented for the electronic structures of copper oxides including $\mathrm{C}{\mathrm{u}}_{2}\mathrm{O}$, CuO, metastable mixed-valence oxide $\mathrm{C}{\mathrm{u}}_{4}{\mathrm{O}}_{3}$. The optical band gap determined by absorption coefficient, structure in valence conduction bands probed photoemission electron energy loss spectroscopies, respectively. results are compared with many-body $GW$ calculations utilizing an additional on-site...
Despite recent advances in exfoliated vdW ferromagnets, the widespread application of 2D magnetism requires a Curie temperature (Tc) above room as well stable and controllable magnetic anisotropy. Here we demonstrate large-scale iron-based material Fe4GeTe2 with Tc reaching ~530 K. We confirmed high-temperature ferromagnetism by multiple characterizations. Theoretical calculations suggested that interface-induced right shift localized states for unpaired Fe d electrons is reason enhanced Tc,...
We report the synthesis and first electronic characterization of an atomically thin two dimensional π-conjugated polymer. Polymerization via Ullmann coupling a tetrabrominated tetrathienoanthracene on Ag(111) in ultra-high vacuum (UHV) produces porous 2D polymer network that has been characterized by scanning tunnelling microscopy (STM). High-resolution X-ray photoelectron spectroscopy (HRXPS) shows reaction proceeds distinct steps: dehalogenation brominated precursor, which begins at room...
Abstract On-surface covalent self-assembly of organic molecules is a very promising bottom–up approach for producing atomically controlled nanostructures. Due to their highly tuneable properties, these structures may be used as building blocks in electronic carbon-based molecular devices. Following this idea, here we report on the structure an ordered array poly(para-phenylene) nanowires produced by surface-catalysed dehalogenative reaction. By scanning tunnelling spectroscopy follow...
An overview of structural, chemical, and electronic properties epitaxial $\mathrm{Ag}∕\mathrm{Au}(111)$ ultrathin films investigated by scanning tunneling microscopy spectroscopy angle-resolved photoelectron is presented. New insights are exhibited: (i) a short-range ordered surface reconstruction clearly observed for deposition at $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$; (ii) self-organized ordering Ag islands obtained $T\ensuremath{\simeq}80\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. In...
Surface-confined polymerization via Ullmann coupling is a promising route to create one- and two-dimensional covalent π-conjugated structures, including the bottom-up growth of graphene nanoribbons. Understanding mechanism reaction necessary provide platform for rationally controlling formation these materials. We use fast X-ray photoelectron spectroscopy (XPS) in kinetic measurements epitaxial surface 1,4-dibromobenzene on Cu(110) devise model based mean field rate equations, involving...
Ullmann coupling is the most common approach to form surface-confined one- and two-dimensional conjugated structures from haloaryl derivatives. The dimensions of formed nanostructures can be controlled by number location halogens within molecular precursors. Our study illustrates that type halogen plays an essential role in design, orientation, extent organometallic polymeric nanostructures. We performed a comparative analysis five 1,4-dihalobenzene molecules containing chlorine, bromine,...
We present an extensive NMR study of the spin-1/2 antiferromagnetic Heisenberg ladder Cu2(C5H12N2)2Cl4 in a magnetic field range 4.5 - 16.7 T. By measuring proton relaxation rate 1/T_1 and varying around critical H_c1 = Delta / g\mu_B 7.5 T, we have studied transition from gapped spin liquid ground state to gapless regime which can be described as Luttinger liquid. identify intermediate T > |H-H_c1|, where dynamics is (possibly) only controlled by T=0 point H_c1.
Epitaxial Ag ultrathin films grown on Cu(111) have been studied by scanning tunneling microscopy and angle-resolved photoemission spectroscopy. In the submonolayer range, spectroscopic measurements reveal existence of two parabolic dispersive surface bands associated with Cu terraces islands suggesting lateral confinement electronic states. A thickness dependence surface-state energy is evidenced. Moreover, well-known atomic reconstructions (moir\'e triangular superstructures which depend...
Spin-valley magnetic ordering is restricted to layered van der Waals type transition-metal dichalcogenides with temperatures below 55 K. Recent theoretical studies on non-van structures have predicted spin-valley polarization induced semiconducting ferromagnetic ground states, but experimental validation missing. We report high-Curie temperature (TC ~ 225 K) metallic ferromagnetism spontaneous in monolayer Cr2Se3 graphene. Angle-resolved photoemission spectroscopy (ARPES) reveals systematic...
We present a detailed photoemission study of the surface state dispersion in 0--10 ML thin Ag films on Au(111). The $L$-gap Shockley-type changes monotonically from one Au towards with increasing layer thickness indicating an extension wave function into solid. High resolution (PES) enables insight decreasing spin-orbit splitting Ag-covered-Au(111). data have been well reproduced by ab initio band structure calculations using WIEN2K code. dependence binding energy silver film is indicative...
Ullmann coupling or, more generally, dehalogenative aryl-aryl coupling, is one of the most widely exploited chemical reactions to obtain one- and two-dimensional polymers on metal surfaces. It generally described as a two-step reaction: (i) dehalogenation, resulting in formation stable intermediate organometallic phase subsequent (ii) C-C coupling. The topology polymer depends number positions halogen atoms haloaromatic precursor, although its orientation order are determined by structure...
The ${}^{1}\mathrm{H}$ hyperfine shift $K$ and NMR relaxation rate ${T}_{1}^{\ensuremath{-}1}$ have been measured as a function of temperature in the $S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1/2$ Heisenberg antiferromagnetic ladder compound ${\mathrm{Cu}}_{2}({\mathrm{C}}_{5}{\mathrm{H}}_{12}{\mathrm{N}}_{2}{)}_{2}{\mathrm{Cl}}_{4}$. presence spin gap $\ensuremath{\Delta}\ensuremath{\simeq}{J}_{\ensuremath{\perp}}{\ensuremath{-}J}_{\ensuremath{\parallel}}$ this strongly coupled (...
Due to their extreme surface sensitivity, the Shockley states of (111) noble metal surfaces can be used study modifications atomic and electronic properties epitaxial ultra thin films self-organized nanostructures. In metallic interfaces, different parameters state bands (energy, effective mass eventually spin–orbit splitting) have been shown strongly thickness dependent. It was also possible by scanning tunneling spectroscopy evidence a spectroscopic signature buried interfaces. Moreover,...
The inhibition in wave propagation at band gap energies plays a central role many areas of technology such as electronics (electron gaps), nanophotonics (light gaps) and phononics (acoustic among others. Here we demonstrate that metal surfaces featuring free-electron-like bands may become semiconducting by periodic nanostructuration. We combine scanning tunneling spectroscopy angle-resolved photoemisssion to accurately determine the energy-dependent local density states structure Ag/Cu(111)...
We present and analyze the normal phase temperature dependence of resistivity nuclear spin-lattice relaxation $(\mathrm{TMTSF}{)}_{2}{\mathrm{ClO}}_{4}$ under strong transverse magnetic fields. From a field-dependent scaling theory we show that singular enhancement one-dimensional electron-electron umklapp scattering antiferromagnetic spin correlations field play fundamental role in large magnetoresistance Bechgaard salts.
We have studied the modification of Au(111) surface state parameters with Ag deposition. unambiguously evidence a continuous decrease in spin-orbit splitting two subbands upon increasing coverage. An annealing leads to formation chemically disordered Ag-Au alloy. This alloy is accompanied by an increase splitting. established quantitative correlation between amplitude this and relative amount Au atoms probed wave function proving atomic character Control interface allows fine tuning...
We present copper NMR spectra obtained in the high magnetic field phase of inorganic spin-Peierls compound CuGe${\mathrm{O}}_{3}$. In whole range 13-17 T, observed line shapes bring clear evidence for existence a static incommensurate distribution local spin density ${S}_{z}(i)$ corresponding to soliton lattice. The absolute value ${S}_{z}$ at top is found equal 0.065 1.4 K and 16.3 T. temperature dependence amplitude proportional ${(1\ensuremath{-}\frac{T}{{T}_{c}})}^{0.32}$.
We report on the intercalation of a submonolayer copper at 775 K underneath graphene epitaxially grown Ir(111) studied by means low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) 77 K. Nucleation growth dynamics Cu below have been investigated, and, most importantly, mechanism has identified. First, LEED patterns reveal pseudomorphic Ir under topmost layer resulting in large in-plane lattice parameter expansion about 6% compared to Cu(111). Second, large-scale STM...
In the spin-Peierls compound ${\mathrm{CuGeO}}_{3}$, commensurate-incommensurate transition concerning modulation of atomic position and local spin polarization is fully monitored (at $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}4\mathrm{K}$ $\ensuremath{\simeq}$ zero- $T$ limit) by application an external magnetic field $(H)$ above a threshold value ${H}_{c}\ensuremath{\simeq}13\mathrm{T}$. The solitonic profile polarization, as well its absolute magnitude, has been precisely imaged...
Single-crystalline (001) Fe thin films were prepared by molecular beam epitaxy and covered epitaxial MgO barriers. The growth was confirmed to be layer as shown reflection high-energy electron diffraction, which allowed us prepare only two atomic planes of for spin polarization measurements. On the one hand, regular x-ray photoemission spectroscopy measurements evidenced a weak hybridization between O. Moreover, large magnetic moment at interface with circular dichroism These observations...
We conclude from 23Na and 51V NMR measurements in alpha(')-NaxV2O5 (x = 0.996) (i) a charge-ordering transition starting at T</=37 K preceding the lattice distortion (ii) formation of spin gap Delta 106 T(c) 34.7 K. Above T(c), only single Na site is observed agreement with Pmmn space group this first 1/4-filled ladder system. Below K, line evolves into eight distinct quadrupolar split lines, which evidences with, least, doubling unit cell (a,b) plane. A model for unique transition, implying...
The opening of several gaps in the surface band structure vicinal Au(23 23 21) surfaces has been shown by high-resolution photoemission spectroscopy, and energy dependence electron density determined scanning tunneling spectroscopy. From a methodological point view, values phase electronic allow an estimation reconstruction potential, which yields Bragg diffraction, gap formation, modulation density. These spectroscopic behaviors give pedagogical illustration one basic concepts solid state physics.