A5068404573- Magnetic and transport properties of perovskites and related materials
- Physics of Superconductivity and Magnetism
- Electronic and Structural Properties of Oxides
- Advanced Condensed Matter Physics
- Rare-earth and actinide compounds
- Iron-based superconductors research
- Semiconductor materials and devices
- Nuclear Materials and Properties
- Topological Materials and Phenomena
- Inorganic Fluorides and Related Compounds
- High-pressure geophysics and materials
- Superconductivity in MgB2 and Alloys
- Nuclear physics research studies
- Inorganic Chemistry and Materials
- Thermodynamic and Structural Properties of Metals and Alloys
- Geophysics and Sensor Technology
- Organic and Molecular Conductors Research
- 2D Materials and Applications
- Transition Metal Oxide Nanomaterials
- Advanced X-ray and CT Imaging
- Magnetic properties of thin films
- ZnO doping and properties
- Ferroelectric and Piezoelectric Materials
- Graphene research and applications
- Magneto-Optical Properties and Applications
Université Paris-Saclay
2016-2025
Institut des Sciences Moléculaires d'Orsay
2020-2024
ESPCI Paris
2005-2023
University of Illinois Chicago
2008-2023
Centre National de la Recherche Scientifique
2013-2023
Université Paris-Sud
2010-2021
Universidad de Antioquia
2008-2021
Institut National de Physique Nucléaire et de Physique des Particules
2010-2018
Campus France
2018
Mental Health Consumer Survivor Network
2013
We use angle resolved photoemission spectroscopy to study the momentum dependence of superconducting gap in NdFeAsO0.9F0.1 single crystals. find that Gamma hole pocket is fully gapped below transition temperature. The value 15+/-1.5 meV and its anisotropy around smaller than 20% this value-consistent with an isotropic or anisotropic s-wave symmetry order parameter. This a significant departure from situation cuprates, pointing possibility superconductivity iron arsenic based system arises...
We use angle-resolved photoemission spectroscopy to investigate the electronic properties of newly discovered iron-arsenic superconductor ${\mathrm{Ba}}_{1\ensuremath{-}x}{\mathrm{K}}_{x}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ and nonsuperconducting ${\mathrm{BaFe}}_{2}{\mathrm{As}}_{2}$. Our study indicates that Fermi surface undoped, parent compound ${\mathrm{BaFe}}_{2}{\mathrm{As}}_{2}$ consists hole pocket(s) at $\ensuremath{\Gamma}$ (0,0) larger electron $X$ (1,0), in general agreement with...
2D electron systems (2DESs) in functional oxides are promising for applications, but their fabrication and use, essentially limited to SrTiO3 -based heterostructures, hampered by the need growing complex oxide overlayers thicker than 2 nm using evolved techniques. It is demonstrated that thermal deposition of a monolayer an elementary reducing agent suffices create 2DESs numerous oxides.
We study, using angle-resolved photoemission spectroscopy, the two-dimensional electron gas (2DEG) at surface of KTaO${}_{3}$ (KTO), a wide-gap insulator with strong spin-orbit coupling (SOC). find that this 2DEG is genuinely different physical state respect to bulk: orbital symmetries its subbands are entirely reconstructed and their masses renormalized. This occurs because values SOC, Fermi energy, subband splittings become comparable in 2DEG. Additionally, we identify an $F$-center-like...
We report the existence of confined electronic states at (110) and (111) surfaces SrTiO3. Using angle-resolved photoemission spectroscopy, we find that corresponding Fermi surfaces, subband masses, orbital ordering are different from ones (001) surface This occurs because crystallographic symmetries sub-surface planes, electron effective masses along confinement direction, influence symmetry structure t2g manifold. Remarkably, our analysis data also reveals carrier concentration thickness...
Abstract The hybridization between localized 4 f electrons and itinerant in rare-earth-based materials gives rise to their exotic properties like valence fluctuations, Kondo behaviour, heavy-fermions, or unconventional superconductivity. Here we present an angle-resolved photoemission spectroscopy (ARPES) study of the lattice antiferromagnet CeRh 2 Si , where surface bulk Ce-4 spectral responses were clearly resolved. pronounced 0 peak seen for Ce terminated gets strongly suppressed spectra...
Motivated by recent spin- and angular-resolved photoemission (SARPES) measurements of the two-dimensional electronic states confined near (001) surface oxygen-deficient ${\mathrm{SrTiO}}_{3}$, we explore their spin structure means ab initio density functional theory (DFT) calculations slabs. Relativistic nonmagnetic DFT display Rashba-like winding with a splitting few meV when magnetism on Ti ions is included, bands become spin-split an energy difference $\ensuremath{\sim}100\text{ }\text{...
Two-dimensional electron gases (2DEGs) at transition-metal oxide (TMO) interfaces and boundary states in topological insulators, are being intensively investigated. The former system harbors superconductivity, large magneto-resistance ferromagnetism. In the latter, honeycomb-lattice geometry plus bulk spin-orbit interactions lead to topologically protected spin-polarized bands. 2DEGs TMOs with a honeycomb-like structure could yield new of matter, but they had not been experimentally...
We report the existence of metallic two-dimensional electron gases (2DEGs) at (001) and (101) surfaces bulk-insulating TiO2 anatase due to local chemical doping by oxygen vacancies in near-surface region. Using angle-resolved photoemission spectroscopy, we find that electronic structure both is composed two occupied subbands d_xy orbital character. While Fermi surface observed termination isotropic, 2DEG anisotropic shows a charge carrier density three times larger than surface. Moreover,...
We study the effect of oxygen vacancies on electronic structure model strongly correlated metal SrVO$_3$. By means angle-resolved photoemission (ARPES) synchrotron experiments, we investigate systematic UV dose measured spectra. observe onset a spurious dose-dependent prominent peak at an energy range were lower Hubbard band has been previously reported in this compound, raising questions its previous interpretation. careful analysis dependent effects succeed disentangling contributions...
The autocorrelation of angle resolved photoemission data from the high temperature superconductor Bi2Sr2CaCu2O8+d shows distinct peaks in momentum space which disperse with binding energy superconducting state, but not pseudogap phase. Although it is tempting to attribute a non-dispersive behavior some ordering phenomenon, de-construction reveals that arise ordering, rather tips Fermi arcs, themselves do change energy.
The in-plane optical conductivity of Bi2Sr2CaCu2O8 + δ films with small carrier density (underdoped) up to large (overdoped) is derived from accurate reflectivity data. Integrating the increasingly higher frequencies yields energy scale involved in formation condensate. At least underdoped sample, states extending 2 eV contribute superfluid. This anomalously may be assigned a change kinetic at superconducting transition, and compatible an electronic pairing mechanism.
The ab-plane reflectance of Bi2Sr2CaCu2O(8+d) thin films was measured in the 30-25000 cm^(-1) range for one underdoped (Tc = 70 K), and overdoped sample 63 K) as a function temperature (10-300 K). We find qualitatively similar behaviors dependence normal-state infrared response both samples. Above Tc, effective spectral weight, obtained from integrated conductivity, does not decrease when T decreases, so that no opening an optical pseudogap is seen. suggest these are consequences first k=(0,...
In conventional BCS superconductors, the electronic kinetic energy increases upon superfluid condensation (the change DEkin is positive). Here we show that in high critical temperature superconductor Bi-2212, crosses over from a fully compatible behavior (DEkin>0) to an unconventional (DEkin<0) as free carrier density decreases. If single mechanism responsible for superconductivity across whole phase diagram of this should allow smooth transition between such two regimes around optimal doping.
We study, using high-resolution angle-resolved photoemission spectroscopy, the evolution of electronic structure in URu2Si2 at Gamma, Z and X high-symmetry points from high-temperature Kondo-screened regime to low-temperature `hidden-order' (HO) state. At all temperatures symmetry points, we find structures resulting interaction between heavy light bands, related Kondo lattice formation. point, directly measure a hybridization gap 11 meV already open above ordered phase. Strikingly, that...
Spin-orbit interaction and structure inversion asymmetry in combination with magnetic ordering is a promising route to novel materials highly mobile spin-polarized carriers at the surface. Spin-resolved measurements of photoemission current from Si-terminated surface antiferromagnet TbRh_{2}Si_{2} their analysis within an ab initio one-step theory unveil unusual triple winding electron spin along fourfold-symmetric constant energy contours states. A two-band k·p model presented that yields...
Two-dimensional electron gases at oxide surfaces or interfaces show exotic ordered states of matter, like superconductivity, magnetism spin-polarized states, and are a promising platform for alternative oxide-based electronics. Here we directly image dense population randomly distributed ferromagnetic domains ∼40 nm typical sizes room temperature the oxygen-deficient surface SrTiO3, non-magnetic transparent insulator in bulk. We use laser-based photoemission microscopy, an experimental...
${\mathrm{YbNi}}_{4}{\mathrm{P}}_{2}$ is the first known ferromagnetic metal showing a second-order quantum phase transition. Current theoretical understanding rules out criticality in centrosymmetric two- and three-dimensional (2D 3D) metals. Thus, studying electronic structure of prime fundamental importance. Using angle-resolved photoemission spectroscopy, we experimentally prove existence 1D Fermi surface contours. In addition, our results demonstrate that part made states higher...
The in-plane infrared and visible (3 meV-3 eV) reflectivity of Bi2Sr2CaCu2O8+d (Bi-2212) thin films is measured between 300 K 10 for different doping levels with unprecedented accuracy. optical conductivity derived through an accurate fitting procedure. We study the transfer spectral weight from finite energy into superfluid as system becomes superconducting. In over-doped regime, develops at expense states lying below 60 meV, a conventional order few times superconducting gap. underdoped...