Publications de Marco Grioni | EPFL Graph Search

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Resonant inelastic x-ray scattering (RIXS) yields clear evidence of spectroscopic Kondo scales in heavy fermions. In YbInCu4 and YbAgCu4 RIXS probes the Yb2+ component of the hybrid ground state and the temperature dependence of the Yb 4f occupation. We report a sudden valence change at a phase transition in YbInCu4 , but a continuous temperature dependence in YbAgCu4 , consistent with the predictions of the Anderson impurity model, for a Kondo temperature T-K=70 K . These results solve a long-standing cont

Mo8O23 is a low-dimensional chemically robust transition metal oxide coming from a prospective family of functional materials, MoO3-x, ranging from a wide gap insulator (x = 0) to a metal (x = 1). The large number of stoichometric compounds with intermedia ...

We report an angle-resolved photoemission study of the charge stripe ordered La1.6-xNd0.4SrxCuO4 (Nd-LSCO) system. A comparative and quantitative line-shape analysis is presented as the system evolves from the overdoped regime into the charge ordered phase ...

The nature of the Dirac quasiparticles in topological insulators calls for a direct investigation of the electron-phonon scattering at the surface. By comparing time-resolved ARPES measurements of the topological insulator Bi2Se3 with different probing dep ...

We investigate by resonant inelastic x-ray scattering the magnetic excitations in thin films of tetragonal CuO. We identify a spin wave excitation, dispersing on two cupratelike antiferromagnetic sublattices. Its energy at the boundary of the Brillouin zon ...

We performed a photoemission investigation of the electronic structure of PrNiO3 and NdNiO3 through the first order (paramagnetic) metal to (antiferromagnetic) insulator transition. Surprisingly, the data reveal a temperature-dependent loss of spectral weight near the chemical potential, which extends well below the coincident metal-insulator (T-MI) and magnetic (T-Neel) transition temperatures. This is in contrast with the behavior in SmNiO3 and EuNiO3, where the two transitions are separate. The spectral

We studied by angle-resolved photoelectron spectroscopy the strain-related structural transition from a pseudomorphic monolayer (ML) to a striped incommensurate phase in an Ag thin film grown on Pt(111). We exploited the surfactant properties of Bi to grow ordered Pt(111)-xMLAg-Bi trilayers with 0

TaSe3 belongs to a class of low-dimensional materials characterized by the interplay and competition between dimensionality crossover and broken symmetry ground states. A comprehensive study by dc-transport, optical, and angle-resolved photoemission (ARPES) experiments shows that the electronic properties of this compound are strongly anisotropic between the chain and the transverse crystallographic direction. Even though TaSe3 fails to undergo a charge-density-wave (CDW) phase transition, we found evidence

We have measured the resonant inelastic x-ray scattering (RIXS) spectra at the Cu L-3 edge in a variety of cuprates. Exploiting a considerably improved energy resolution (0.8 eV) we recorded significant dependencies on the sample composition and orientation, on the scattering geometry, and on the incident photon polarization. The RIXS final states correspond to two families of electronic excitations, having local (dd excitations) and nonlocal (charge-transfer) character. The dd energy splitting can be estim

We discuss two different approaches for tuning the giant spin-orbit splitting of a BiAg2 surface alloy. The first approach consists of electron doping by alkaline metal deposition in order to shift the energy position of the spin-split surface states, while the second is based on the novel Si(1 1 1)-Ag-BiAg2 trilayer system. In both cases the spin-polarized structure near the Fermi level can be controlled by an external parameter, while the second approach permits coupling the concept of giant spin-splittin

We present spectroscopic data on the electronic structure of YbS under pressure. From resonant x-ray emission and x-ray absorption spectra in the high-resolution partial fluorescence yield mode, we find that the Yb valence increases from 2.3 at ambient pressure to 2.6 at 360 kbar. The accuracy of these estimates is enhanced by a combined analysis of emission spectra measured as a function of the incident and emitted energy. The spectral line shapes reflect the mixed character of the electronic states, inter

We have performed a high-energy-resolution photoelectron spectroscopy investigation of the quasi-two-dimensional material 2H-TaSe2. Temperature-dependent constant-binding energy curves reveal that characteristic changes in the electronic density of states occur continuously through the second-order charge-density-wave (CDW) transition at 122 K. The photoelectron spectra indicate that different parts of the Fermi surface are unequally affected by the CDW and suggest the formation of an energy gap in the GAMM

High-resolution angle-resolved photoemission (ARPES) displays quasi-one dimensional (1D) electronic states in the insulating molybdenum red bronze K0.33MoO3, in good qualitative agreement with band structure calculations. Combined ARPES, optical conductivity, and electrical resistivity data underline the importance of defects which pin the Fermi level within the gap. The ARPES line shape exhibits the same strong-coupling features observed in the blue bronze K0.3MoO3, a related 1D Peierls conductor. We specu

We present a combined angle-resolved photoemission spectroscopy and resistivity study of the model Fermi liquid system 1T-TiTe2. From the analysis of the quasiparticle spectral line shape we identify and separately evaluate the electron-electron. electron-phonon, and impurity scattering contributions to the quasiparticle lifetime. There is a clear correspondence between spectroscopic and transport data. A residual low-temperature spectral linewidth (Gamma (o)=17 meV) indicates that the three-dimensional nat

We have studied by high resolution ARPES the spectroscopic properties of the prototype charge density wave system (TaSe4)(2)I and of the closely related insulating compound (NbSe4)(3)I. We observe features dispersing with the lattice periodicity, including commensurate (in (NbSe4)(3)I) and incommensurate (in (TaSe4)(2)I) superlattice shadow bands. The spectral lineshape is anomalous in the normal metallic state, and the intensity is strongly suppressed near the Fermi surface. In the insulating CDW state the

Optical and photoemission experiments reveal unexpected spectral signatures of one-dimensional band insulators. In the model compound (NbSe4)(3)I the optical conductivity decays as a power law sigma(1)(omega) similar to omega(-4.25) above a sharp gap edge. Photoemission observes both the valence and a shadow band, produced w by a commensurate superstructure. We identify an optical and photoemission band gap consistent with other measurements but much smaller than the energy scale defined by the dispersion o

In order to exploit the intriguing optical properties of graphene it is essential to gain a better understanding of the light-matter interaction in the material on ultrashort timescales. Exciting the Dirac fermions with intense ultrafast laser pulses trigg ...

We report on angle-resolved photoemission and superconductor-insulator-superconductor tunneling measurements of the normal and superconducting states of Bi2Sr2CaCu2O8+x single crystal samples and Bi2Sr2CaCu2O8+x - native oxide- lead (S-I-S) tunnel junctions.

Photoelectron spectroscopy with very high energy resolution reveals both dramatic and subtle changes in the electronic density of states of the quasi-2D material 1T-TaS2, in coincidence with transitions between different charge density wave phases. Our results are consistent with the occurrence of a zero-gap Mott transition at approximately 185 K and of a subsequent Anderson localization in the pseudogap between the Hubbard subbands, and provide new insight into the unusual electronic properties of this mat

Photoelectron spectroscopy with high-energy resolution has been utilized to investigate the charge-density wave (CDW) in 1T-TaS2 between 20 and 360 K. Constant binding-energy curves reveal discontinuities in the temperature dependence of the photoelectron spectral function rho(E), and demonstrate that sudden modifications of the electronic structure, namely, in the vicinity of the Fermi level E(F), mark the first-order CDW transitions. In the commensurate phase, below 180 K, rho(E(F)) reflects the formation

Marco Grioni

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New spectroscopy solves an old puzzle: The Kondo scale in heavy fermions

Unveiling the electronic transformations in the semi-metallic correlated-electron transitional oxide Mo8O23

Electron scattering, charge order, and pseudogap physics in La1.6-xNd0.4SrxCuO4: An angle-resolved photoemission spectroscopy study

Evidence of reduced surface electron-phonon scattering in the conduction band of Bi2Se3 by nonequilibrium ARPES

Magnons in tetragonal CuO

Electronic-structure evolution through the metal-insulator transition in RNiO3

Ag-coverage-dependent symmetry of the electronic states of the Pt(111)-Ag-Bi interface: The ARPES view of a structural transition

Spectroscopic and dc-transport investigations of the electronic properties of TaSe3

Low energy electronic excitations in the layered cuprates studied by copper L-3 resonant inelastic X-ray scattering

Tuning the giant Rashba effect on a BiAg2 surface alloy: Two different approaches

Valence of YbS under pressure: A resonant inelastic x-ray emission study

Spectroscopic Observation Of Charge-Density-Wave-Induced Changes In The Electronic-Structure Of 2H-TaSe2

Electronic structure of a quasi-one-dimensional insulator: The molybdenum red bronze K0.33MoO3

High-resolution angle-resolved photoemission investigation of the quasiparticle scattering processes in a model Fermi liquid: 1T-TiTe2

The spectroscopic properties of 1D Peierls systems

Dynamical properties of the one-dimensional band insulator (NbSe4)(3)I

Ultrafast electron dynamics in epitaxial graphene investigated with time- and angle-resolved photoemission spectroscopy

Doping dependence of electronic structure in Bi2Sr2CaCu2O8+x

High-Resolution Photoemission Investigation Of Phase-Transitions In 1T-Tas2

Spectroscopic Signatures Of Phase-Transitions In A Charge-Density-Wave System - 1T-Tas2