104 research outputs found
Atomic and Electronic Structure of a Rashba - Junction at the BiTeI Surface
The non-centrosymmetric semiconductor BiTeI exhibits two distinct surface
terminations that support spin-split Rashba surface states. Their ambipolarity
can be exploited for creating spin-polarized - junctions at the
boundaries between domains with different surface terminations. We use scanning
tunneling microscopy/spectroscopy (STM/STS) to locate such junctions and
investigate their atomic and electronic properties. The Te- and I-terminated
surfaces are identified owing to their distinct chemical reactivity, and an
apparent height mismatch of electronic origin. The Rashba surface states are
revealed in the STS spectra by the onset of a van Hove singularity at the band
edge. Eventually, an electronic depletion is found on interfacial Te atoms,
consistent with the formation of a space charge area in typical -
junctions.Comment: 5 pages, 4 figure
Giant alkali-metal-induced lattice relaxation as the driving force of the insulating phase of alkali-metal/Si(111):B
Ab initio density-functional theory calculations, photoemission spectroscopy (PES), scanning tunneling microscopy, and spectroscopy (STM, STS) have been used to solve the 2√3 x 2√3R30 surface reconstruction observed previously by LEED on 0.5 ML K/Si:B. A large K-induced vertical lattice relaxation occurring only for 3/4 of Si adatoms is shown to quantitatively explain both the chemical shift of 1.14 eV and the ratio 1/3 measured on the two distinct B 1s core levels. A gap is observed between valence and conduction surface bands by ARPES and STS which is shown to have mainly a Si-B character. Finally, the calculated STM images agree with our experimental results. This work solves the controversy about the origin of the insulating ground state of alkali-metal/Si(111):B semiconducting interfaces which were believed previously to be related to many-body effectsThis work has received the financial support of the French ANR SURMOTT program (ANR-09-BLAN- 0210-01) and the Spanish MICIIN under Project No. FIS2010-1604
Ce-L3-XAS study of the temperature dependence of the 4f occupancy in the Kondo system Ce2Rh3Al9
We have used temperature dependent x-ray absorption at the Ce-L3 edge to
investigate the recently discovered Kondo compound Ce2Rh3Al9. The systematic
changes of the spectral lineshape with decreasing temperature are analyzed and
found to be related to a change in the occupation number, n_f, as the
system undergoes a transition into a Kondo state. The temperature dependence of
indicates a characteristic temperature of 150K, which is clearly related
with the high temperature anomaly observed in the magnetic susceptibility of
the same system. The further anomaly observed in the resistivity of this system
at low temperature (ca. 20K) has no effect on n_f and is thus not of Kondo
origin.Comment: 7 pages, three figures, submitted to PR
Self-ordered nanoporous lattice formed by chlorine atoms on Au(111)
A self-ordered nanoporous lattice formed by individual chlorine atoms on the Au(111) surface has been studied with low-temperature scanning tunneling microscopy, low-energy electron diffraction, and density functional theory calculations. We have found out that room-temperature adsorption of 0.09–0.30 monolayers of chlorine on Au(111) followed by cooling below 110 K results in the spontaneous formation of a nanoporous quasihexagonal structure with a periodicity of 25–38 Å depending on the initial chlorine coverage. The driving force of the superstructure formation is attributed to the substrate-mediated elastic interaction
Low-temperature coherence in the periodic Anderson model: Predictions for photoemission of heavy Fermions
We present numerically exact predictions of the periodic and single-impurity
Anderson models to address photoemission experiments on heavy Fermion systems.
Unlike the single impurity model the lattice model is able to account for the
enhanced intensity, dispersion, and apparent weak temperature dependence of the
Kondo resonant peak seen in recent controversial photoemission experiments. We
present a consistent interpretation of these results as a crossover from the
impurity regime to an effective Hubbard model regime described by Nozieres.Comment: 4 pages, 3 figure
High-resolution Ce 3d-edge resonant photoemission study of CeNi_2
Resonant photoemission (RPES) at the Ce 3d -> 4f threshold has been performed
for alpha-like compound CeNi_2 with extremely high energy resolution (full
width at half maximum < 0.2 eV) to obtain bulk-sensitive 4f spectral weight.
The on-resonance spectrum shows a sharp resolution-limited peak near the Fermi
energy which can be assigned to the tail of the Kondo resonance. However, the
spin-orbit side band around 0.3 eV binding energy corresponding to the f_{7/2}
peak is washed out, in contrast to the RPES spectrum at the Ce 3d -> 4f RPES
threshold. This is interpreted as due to the different surface sensitivity, and
the bulk-sensitive Ce 3d -> 4f RPES spectra are found to be consistent with
other electron spectroscopy and low energy properties for alpha-like
Ce-transition metal compounds, thus resolves controversy on the interpretation
of Ce compound photoemission. The 4f spectral weight over the whole valence
band can also be fitted fairly well with the Gunnarsson-Schoenhammer
calculation of the single impurity Anderson model, although the detailed
features show some dependence on the hybridization band shape and (possibly) Ce
5d emissions.Comment: 4 pages, 3 figur
Ultrafast Atomic Diffusion Inducing a Reversible (2√3×2√3)R30°↔(√3×√3)R30° Transition on Sn/Si(111)∶B
Dynamical phase transitions are a challenge to identify experimentally and describe theoretically. Here, we study a new reconstruction of Sn on silicon and observe a reversible transition where the surface unit cell divides its area by a factor of 4 at 250 °C. This phase transition is explained by the 24-fold degeneracy of the ground state and a novel diffusive mechanism, where four Sn atoms arranged in a snakelike cluster wiggle at the surface exploring collectively the different quantum mechanical ground states.This work was supported by the French Agence Nationale de la Recherche (ANR) under Contract SurMott, No. NT-09-618999, and by Spanish Ministerio de EconomÃa y Competitividad, Project No. MAT2014-59966-R
Electronic structure investigation of CeB6 by means of soft X-ray scattering
The electronic structure of the heavy fermion compound CeB6 is probed by
resonant inelastic soft X-ray scattering using photon energies across the Ce 3d
and 4d absorption edges. The hybridization between the localized 4f orbitals
and the delocalized valence-band states is studied by identifying the different
spectral contributions from inelastic Raman scattering and normal fluorescence.
Pronounced energy-loss structures are observed below the elastic peak at both
the 3d and 4d thresholds. The origin and character of the inelastic scattering
structures are discussed in terms of charge-transfer excitations in connection
to the dipole allowed transitions with 4f character. Calculations within the
single impurity Anderson model with full multiplet effects are found to yield
consistent spectral functions to the experimental data.Comment: 9 pages, 4 figures, 1 table,
http://link.aps.org/doi/10.1103/PhysRevB.63.07510
Anomalous spectral weight in photoemission spectra of the hole doped Haldane chain Y2-xSrxBaNiO5
In this paper, we present photoemission experiments on the hole doped Haldane
chain compound . By using the photon energy dependence of
the photoemission cross section, we identified the symmetry of the first
ionisation states (d type). Hole doping in this system leads to a significant
increase in the spectral weight at the top of the valence band without any
change in the vicinity of the Fermi energy. This behavior, not observed in
other charge transfer oxides at low doping level, could result from the
inhomogeneous character of the doped system and from a Ni 3d-O 2p hybridization
enhancement due to the shortening of the relevant Ni-O distance in the
localized hole-doped regions.Comment: 5 pages, 4 figure
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