Publications de Helmuth Berger

Chattez avec Graph Search

Posez n’importe quelle question sur les cours, conférences, exercices, recherches, actualités, etc. de l’EPFL ou essayez les exemples de questions ci-dessous.

AVERTISSEMENT : Le chatbot Graph n'est pas programmé pour fournir des réponses explicites ou catégoriques à vos questions. Il transforme plutôt vos questions en demandes API qui sont distribuées aux différents services informatiques officiellement administrés par l'EPFL. Son but est uniquement de collecter et de recommander des références pertinentes à des contenus que vous pouvez explorer pour vous aider à répondre à vos questions.

We studied the deposition of Au, In, Ag, and Al overlayers onto clean-cleaved GaTe(001) surfaces at room temperature by x-ray photoelectron spectroscopy. Gold and In overlayers did not produce evidence of chemical reactions, and neither with cation nor anion outdiffusion. Gold overlayers exhibited no evidence of island formation and a layer-by-layer overlayer coverage. The deposition of In revealed the presence of clustering for a metal thickness higher than 6 Angstrom. On the other hand, the deposition of

The prospect of optically inducing and controlling a spin-polarized current in spintronic devices has generated wide interest in the out-of-equilibrium electronic and spin structure of topological insulators. In this Letter we show that only measuring the ...

When thinned down to the atomic scale, many layered van der Waals materials exhibit an interesting evolution of their electronic properties, whose main aspects can be accounted for by changes in the single-particle bandstructure. Phenomena driven by intera ...

The plasmon dispersion in 2H transition metal dichalcogenides has been reported to be negative, which is a strong renormalization with respect to the expectations for a homogeneous electron gas. This has been interpreted to be either due to the interaction ...

We revisit charge density wave (CDW) behavior in the archetypal quasi-one-dimensional (quasi-1D) material NbSe3 by high-resolution angle-resolved photoemission spectroscopy measurements utilizing a microfocused laser with a photon energy of 6.3 eV. We pres ...

We examine the experimental and theoretical electron-energy loss spectra in 2H-Cu0.2NbS2 and find that the 1 eV plasmon in this material does not exhibit the regular positive quadratic plasmon dispersion that would be expected for a normal broad-parabolic- ...

In this Letter we report the observation, by scanning tunneling microscopy, of a Mott metal to insulator transition at the surface of 1T-TaSe2. Our spectroscopic data compare considerably well with previous angle-resolved photoemission spectroscopy measure ...

Frustrated spin-1/2 chains, despite the apparent simplicity, exhibit a remarkably rich phase diagram comprising vector-chiral (VC), spin-density-wave (SDW), and multipolar/spin-nematic phases as a function of the magnetic field. Here we report a study of b ...

We report on the ab-plane optical reflectance measurements of single crystals of Y-doped Bi2Sr2CaCu2O8+delta and Pr-doped YBa2Cu3O7-delta over a wide frequency range from 80 to 40 000 cm(-1) (10 meV-5 eV) and at temperatures between 20 and :300 K. Y and Pr doping both decrease the hole concentration in the CuO2 planes. This has allowed us to investigate the evolution of ab-plane charge dynamics at doping levels ranging from heavily underdoped to nearly optimally doped. Our results of the low-frequency optic

Nanoscale chiral skyrmions in noncentrosymmetric helimagnets are promising binary state variables in high-density, low-energy nonvolatile memory. Skyrmions are ubiquitous as an ordered, single-domain lattice phase, which makes it difficult to write informa ...

We report resistivity and thermo-electric power measurements of the anatase phase of TiO2 under pressure up to 2.3 GPa. Despite its transparent appearance, the single crystal of anatase exhibits a metallic-like resistivity above 60 K, at all pressures. The ...

A detailed zero-and transverse-field muon spin rotation investigation of magnetism and the magnetoelectric coupling in Cu2OSeO3 is reported. An internal magnetic field B-int(T = 0) = 85.37(25) mT was found, in agreement with a ferrimagnetic state below T-c ...

A detailed synchrotron X-ray diffraction (XRD) study performed with a single crystal of BaVS3 (barium vanadium trisulfide) in the temperature range between 10 and 295 K is reported. Aside from the known tetragonal–orthorhombic (240 K) and orthorhombic–mono ...

Inelastic electron scattering is applied to investigate the impact of potassium intercalation on the charge-carrier plasmon energy and dispersion in the charge- density wave (CDW) bearing compound 2H-TaSe2. We observe an unususal doping dependence of the p ...

A comparative study has been made of iodine-intercalated Bi2Sr2Ca1Cu2Ox single crystal and 1 atm O2 annealed Bi2Sr2Ca1Cu1Ox single crystal using an AC susceptibility measurement, X-ray photoemission (XPS) and angle-resolved ultraviolet photoemission spectroscopy (ARUPS). The AC susceptibility measurement indicates that O2 doped samples studied have a T(c) of 84 K, whereas T(c) of the iodine-doped samples studied are 80 K. XPS Cu 2p core-level data establish that the hole concentration in the CuO2 planes is

Superconductivity in high-Tc cuprates is particularly sensitive to disorder due to the unconventional d-wave pairing symmetry. We investigated effects of disorder on the spectral properties of Bi2Sr2CaCu2O8+x high-Tc superconductor. We found that already small defect densities suppress the characteristic spectral signature of the superconducting state. The spectral line shape clearly reflects new excitations within the gap, as expected for de

Macroscopic quantum phenomena such as high-temperature superconductivity, colossal magnetoresistance, ferrimagnetism and ferromagnetism arise from a delicate balance of different interactions among electrons, phonons and spins on the nanoscale(1). The stud ...

We present infrared and Raman measurements of magnetite (Fe3O4). This material is known to undergo a metal-insulator and a structural transition (Verwey transition) at T-V = 120 K. The structural aspect of the Verwey transition is disclosed by the appearance of additional infrared-active and Raman-active phonons. The frequencies of the infrared-active phonons show no significant singularities at the transition whereas their linewidths increase. The frequency and linewidth of the Raman-active phonon at 670 c

We report a combined theoretical and experimental investigation devoted to getting deeper insights into the exotic magnetic properties of the low-dimensional SeCuO3 system, for which the two inequivalent Cu(1) and Cu(2) sites show different quantum dynamic ...

Detailed data on the momentum-resolved temperature dependence of the superconducting gap of Bi2Sr2CaCu2O8+x are presented, complemented by similar data on the intensity of the photoemission superconducting condensate spectral area. The gap anisotropy between the Gamma-(M) over bar and Gamma-X directions increases markedly with increasing temperature, contrary to what happens for conventional anisotropic-gap superconductors, such as lead. Specifically, the size of the superconducting gap along the Gamma-X di

Helmuth Berger

Chattez avec Graph Search

Schottky barrier and interface formation of metal-GaTe(001) interfaces

Momentum-Resolved Spin Dynamics of Bulk and Surface Excited States in the Topological Insulator Bi2Se3

Gate-induced superconductivity in atomically thin MoS2 crystals

Unscreened plasmon dispersion of 2H transition metal dichalcogenides

Role of a higher-dimensional interaction in stabilizing charge density waves in quasi-one-dimensional NbSe3 revealed by angle-resolved photoemission spectroscopy

Negative plasmon dispersion in 2H-NbS2 beyond the charge-density-wave interpretation

Mott phase at the surface of 1T-TaSe2 observed by scanning tunneling microscopy

Magnetic ground state of the frustrated spin-1/2 chain compound beta-TeVO4 at high magnetic fields

Doping-induced change of optical properties in underdoped cuprate superconductors

Imaging and manipulation of skyrmion lattice domains in Cu2OSeO3

High-pressure study of anatase TiO2

mu SR investigation of magnetism and magnetoelectric coupling in Cu2OSeO3

One-dimensional composite host-guest structure in BaVS3

Doping dependence of the plasmon dispersion in 2H-TaSe2

Effect of Iodine Doping on Bi2Sr2Ca1Cu2Ox - Charge-Transfer or Interlayer Coupling

Defect-induced changes in the spectral properties of high-Tc cuprates

Snapshots of cooperative atomic motions in the optical suppression of charge density waves

Infrared and Raman studies of the Verwey transition in magnetite

Coherent description of the magnetic properties of SeCuO3 versus temperature and magnetic field

Temperature-Dependence of the Superconducting Gap Anisotropy in Bi2Sr2CaCu2O8+X