A5091567637- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Rare-earth and actinide compounds
- Iron-based superconductors research
- Advanced Thermoelectric Materials and Devices
- Chalcogenide Semiconductor Thin Films
- Ferroelectric and Piezoelectric Materials
- Thermodynamic and Structural Properties of Metals and Alloys
- Electronic and Structural Properties of Oxides
- Quantum, superfluid, helium dynamics
- Quantum and electron transport phenomena
- Semiconductor materials and devices
- Multiferroics and related materials
- Hydrogen Storage and Materials
- Laser-Matter Interactions and Applications
- Spectroscopy and Quantum Chemical Studies
- 2D Materials and Applications
- Microwave Dielectric Ceramics Synthesis
- Inorganic Chemistry and Materials
- Spectroscopy and Laser Applications
Laboratoire Interdisciplinaire Carnot de Bourgogne
2024
Oak Ridge National Laboratory
2005-2012
United States Naval Research Laboratory
2004
and are closely related materials on opposite sides of a ferromagnetic quantum critical point. The Stoner factor Ni is virtually the same in both compounds density states larger . Thus theory it should be more magnetic, local-density approximation (LDA) calculations is. However, experimentally paramagnet, while an itinerant ferromagnet. We show that spin fluctuations stronger , due to weaker dependence susceptibility, this effect enough reverse trend. approach combines LDA with Landau...
The first members of the series intergrowth ${\text{PbSe-WSe}}_{2}$ compounds are investigated using first-principles electronic-structure calculations and Boltzmann transport theory. These materials moderate band-gap semiconductors. valence-band edges primarily derived from PbSe-derived states while conduction bands have mixed character. show that high thermopowers attainable at to $p$-type doping levels, consistent with good thermoelectric performance temperatures 300 1000 K.
Density functional calculations of the fermiology and magnetic properties $\mathrm{C}{\mathrm{a}}_{3}\mathrm{R}{\mathrm{u}}_{2}{\mathrm{O}}_{7}$ reveal an unusual state: a bulk spin valve. The ground state consists nearly half-metallic bilayers stacked antiferromagnetically with weak coupling. Out plane transport is very strongly suppressed by antiferromagnetic alignment, which can be destroyed in favor ferromagnetism at low energy cost. Furthermore, ferromagnetic highly unusual; opposite...
The puzzle of three-dimensional magnetic interactions in the structurally two-dimensional layered-oxide ${\mathrm{Na}}_{x}{\mathrm{CoO}}_{2}$ is addressed using first-principles calculations and an analysis exchange mechanisms. agree with recent neutron results, favoring antiferromagnetic stacking ferromagnetic planes. superexchange via direct O-O hopping through intermediate Na $s{p}^{2}$ hybrids couples each Co to its nearest six next-nearest interplanar neighbors equivalent paths....
We report an extensive study on the intrinsic bulk electronic structure of high-temperature superconductor ${\text{CeFeAsO}}_{0.89}{\text{F}}_{0.11}$ and its parent compound CeFeAsO by soft hard x-ray photoemissions, absorption, emission spectroscopies. The complementary surface/bulk probing depth, elemental chemical sensitivity these techniques allow resolving each element correlating it with local structure, which has been probed extended absorption fine-structure spectroscopy....
We show using density functional calculations that the small ${e}_{g}^{\ensuremath{'}}$ Fermi surfaces in ${\mathrm{Na}}_{x}{\mathrm{CoO}}_{2}$ are destroyed by Na disorder. This provides a means to resolve prediction of these sections band structure with their nonobservation angle resolved photoemission experiments.
For over three decades, the infrared spectroscopy peaks of around 3500 cm${}^{\ensuremath{-}1}$ observed in hydrogen-doped SrTiO${}_{3}$ samples have been assigned to an interstitial hydrogen (H${}_{i}$) attached a lattice oxygen with two possible configuration models: octahedral edge (OE) and cubic face (CF) models. Based on our first-principles calculations H${}_{i}$ O, both OE CF configurations are not energetically stable. Starting from either configuration, would spontaneously relax...
The orbital symmetries of electron-doped iron-arsenide superconductors $\text{Ba}{({\text{Fe}}_{1\ensuremath{-}x}{\text{Co}}_{x})}_{2}{\text{As}}_{2}$ have been measured with x-ray absorption spectroscopy. data reveal signatures $\text{Fe}\text{ }d$ electron itinerancy, weak electronic correlations, and a high degree Fe-As hybridization related to the bonding topology }{d}_{\text{xz}+\text{yz}}$ states, which are found contribute substantially at Fermi level. energies detailed character Fe...
We report an electrical transport study in ${\mathrm{Ca}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{RuO}}_{4}$ single crystals at high magnetic fields ($B$). For $x=0.2$, the Hall constant ${R}_{xy}$ decreases sharply anisotropic metamagnetic transition, reaching its value for ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$ fields. A sharp decrease $A$ coefficient of resistivity ${T}^{2}$ term and a change structure angular magnetoresistance oscillations $B$ rotating planes confirms reconstruction...
First-principles supercell calculations are used to investigate the lattice distortions in ${\text{BaZrO}}_{3}$ heavily codoped with K and La. We find that nonferroelectric can be made ferroelectric this way. The ferroelectricity is result of La off-centerings understood using ionic size considerations. In particular, disorder on perovskite $A$ site suppresses tendency toward octahedral tilts substitution small ion. This results $A$-site driven ferroelectricity.
Density functional calculations of the electronic structure are used to elucidate bonding . It is found that this material best described as ionic, and in particular units not reasonably viewed substantially covalent.
We demonstrate the generation of a persistent planar molecular alignment by subjecting relatively warm gas sample to resonant femtosecond laser pulse. By optically probing I_{2} molecules in their vibronic ground states, we observe delocalization axes near plane orthogonal field direction. This phenomenon is attributed one-photon excitation, primarily removing from thermal ground-state distribution that are initially aligned along field, i.e., those with small projection rotational angular...