A5065167091- Magnetic and transport properties of perovskites and related materials
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Advanced Thermoelectric Materials and Devices
- Thermal properties of materials
- Multiferroics and related materials
- X-ray Diffraction in Crystallography
- High-pressure geophysics and materials
- Electronic and Structural Properties of Oxides
- Crystallization and Solubility Studies
- Phase-change materials and chalcogenides
- Ferroelectric and Piezoelectric Materials
- Rare-earth and actinide compounds
- Iron-based superconductors research
- Superconductivity in MgB2 and Alloys
- Magnetic properties of thin films
- Quasicrystal Structures and Properties
- Diamond and Carbon-based Materials Research
- Thermodynamic and Structural Properties of Metals and Alloys
- Glass properties and applications
- Boron and Carbon Nanomaterials Research
- ZnO doping and properties
- Semiconductor materials and devices
- Advanced ceramic materials synthesis
- Gas Sensing Nanomaterials and Sensors
Université Claude Bernard Lyon 1
2015-2024
Centre National de la Recherche Scientifique
2015-2024
Institut Lumière Matière
2015-2024
Conservatoire National des Arts et Métiers
2023
Centre d'Énergétique et de Thermique de Lyon
2023
Institut National des Sciences Appliquées de Lyon
2023
Laboratoire Énergies et Mécanique Théorique et Appliquée
2023
Université de Lorraine
2023
Forum Réfugiés - Cosi
2015-2020
Paul Scherrer Institute
2007-2015
One of the leading issues in high-${T}_{C}$ superconductors is origin pseudogap phase underdoped cuprates. Using polarized elastic neutron diffraction, we identify a novel magnetic order ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6+x}$ system. The observed preserves translational symmetry lattice as proposed for orbital moments circulating current theory state. To date, it first direct evidence hidden parameter characterizing
Through a systematic structural search we found an allotrope of carbon with Cmmm symmetry which predict to be more stable than graphite for pressures above 10 GPa. This material, refer as Z-carbon, is formed by pure sp(3) bonds and it provides explanation several features in experimental x-ray diffraction Raman spectra under pressure. The transition from Z-carbon can occur through simple sliding buckling graphene sheets. Our calculations that transparent wide band-gap semiconductor hardness...
An unusual spin excitation mode observed by neutron scattering has inspired numerous theoretical studies of the interplay between charged quasiparticles and collective excitations in copper oxide high-temperature superconductors. The has, thus far, only been materials with crystal structures consisting bilayers, it is absent single-layer compound La(2-x)Sr(x)CuO(4+delta). Neutron-scattering data now show that present Tl(2)Ba(2)CuO(6+delta), a superconducting transition temperature...
We have performed high-resolution neutron diffraction and inelastic scattering experiments in the frustrated multiferroic hexagonal compounds $R{\mathrm{MnO}}_{3}$ ($R=\mathrm{Ho},\mathrm{Yb},\mathrm{Sc},\mathrm{Y}$), which provide evidence of a strong magnetoelastic coupling whole family. can correlate atomic positions, type magnetic structure, nature spin waves whatever $R$ ion temperature. The key parameter is position Mn ions unit cell with respect to critical threshold $1/3$, determines...
Perfectly crystalline solids are excellent heat conductors. Prominent counterexamples intermetallic clathrates, guest-host systems with a high potential for thermoelectric applications due to their ultralow thermal conductivities. Our combined experimental and theoretical investigation of the lattice dynamics particularly simple binary representative, ${\mathrm{Ba}}_{8}{\mathrm{Si}}_{46}$, identifies mechanism responsible reduction conductivity intrinsic perfect crystal structure. Above...
Engineering lattice thermal conductivity requires to control the heat carried by atomic vibration waves, phonons. The key parameter for quantifying it is phonon lifetime, limiting travelling distance, whose determination however at limits of instrumental capabilities. Here, we show achievement a direct quantitative measurement lifetimes in single crystal clathrate Ba7.81Ge40.67Au5.33, renowned its puzzling 'glass-like' conductivity. Surprisingly, transport dominated acoustic phonons with...
The ability of some materials with a perfectly ordered crystal structure to mimic the heat conduction amorphous solids is remarkable physical property that finds applications in numerous areas science, for example, search more efficient thermoelectric enable directly convert into electricity. Here, we unveil mechanism which glass-like thermal conductivity emerges tetrahedrites, family natural minerals extensively studied geology and, recently, thermoelectricity. By investigating lattice...
We report the results of a combined muon-spin rotation and neutron-scattering study on ${\text{La}}_{2\ensuremath{-}x}{\text{Sr}}_{x}{\text{CuO}}_{4}$ in vicinity so-called 1/8 anomaly. Application magnetic field drives system toward magnetically ordered spin-density-wave state, which is fully developed at doping. The are discussed terms competition between antiferromagnetic superconducting order parameters.
Inelastic neutron scattering measurements have been performed on YMnO3, aiming to study the interplay between spin and lattice degrees of freedom in this hexagonal multiferroic material. Our provides evidence for a strong coupling magnons phonons, evidenced by opening gap below T(N) dispersion transverse acoustic phonon mode polarized along ferroelectric axis. The resulting upper branch is found lock one spin-wave modes. These findings are discussed terms possible hybridization two types...
One of the key requirements for good thermoelectric materials is a low lattice thermal conductivity. Here we present combined neutron scattering and theoretical investigation dynamics in type I clathrate system Ba-Ge-Ni, which fulfills this requirement. We observe strong hybridization between phonons Ba guest atoms acoustic Ge-Ni host structure over wide region Brillouin zone, contrast with frequently adopted picture isolated cages. It occurs without decrease phonon lifetime, contradicts...
A detailed inelastic neutron scattering study of the high temperature superconductor $\rm YBa_2Cu_3O_{6.85}$ provides evidence new resonant magnetic features, in addition to well known mode at 41 meV: (i) a commensurate resonance peak 53 meV with an even symmetry under exchange two adjacent CuO_2$ layers; and (ii) energy incommensurate spin excitations whose spectral weight is around 54 meV. The locus these modes can be understood by considering momentum shape electron-hole spin-flip...
We present angle-resolved photoemission spectroscopy data on moderately underdoped ${\mathrm{La}}_{1.855}{\mathrm{Sr}}_{0.145}{\mathrm{CuO}}_{4}$ at temperatures below and above the superconducting transition temperature. Unlike previous studies of this material, we observe sharp spectral peaks along entire underlying Fermi surface in state. These trace out an energy gap that follows a simple $d$-wave form, with maximum 14 meV. Our results are consistent single picture for cuprates....
The magnetic ordering of the hexagonal multiferroic compound ${\text{YbMnO}}_{3}$ has been studied between 100 and 1.5 K by combining neutron powder diffraction, $^{170}\text{Y}\text{b}$ M\"ossbauer spectroscopy, magnetization measurements. Yb moments two crystallographic sites order at different temperatures: $4b$ site together with Mn (at ${T}_{N}\ensuremath{\simeq}85\text{ }\text{K}$) $2a$ well below 3.5 K). temperature dependences are explained within a molecular-field model, showing...
Ab initio studies have theoretically predicted room-temperature ferromagnetism in crystalline ${\text{SnO}}_{2}$, ${\text{ZrO}}_{2}$, and ${\text{TiO}}_{2}$ doped with nonmagnetic element from the 1A column as K Na. Our purpose is to address experimentally possibility of magnetism both ${\text{Sn}}_{1\ensuremath{-}x}{\text{K}}_{x}{\text{O}}_{2}$ ${\text{Sn}}_{1\ensuremath{-}x}{\text{Ca}}_{x}{\text{O}}_{2}$ compounds. The samples been prepared using equilibrium methods standard solid-state...
We report an angle-resolved photoemission study of the charge stripe ordered ${\mathrm{La}}_{1.6\ensuremath{-}x}{\mathrm{Nd}}_{0.4}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ (Nd-LSCO) system. A comparative and quantitative line-shape analysis is presented as system evolves from overdoped regime into phase. On side ($x=0.20$), a normal-state antinodal spectral gap opens upon cooling below 80 K. In this process, weight preserved but redistributed to larger energies. correlation between electron...
The observation of an unusual spin resonant excitation in the superconducting state various High-Tc ~copper oxides by inelastic neutron scattering measurements is reviewed. This magnetic mode % (that does not exist conventional superconductors) discussed light a few theoretical models and likely corresponds to spin-1 collective mode.
In high-temperature copper oxide superconductors, a novel magnetic order associated with the pseudogap phase has been identified in two different cuprate families over wide region of temperature and doping. We report here observation below 120 K similar ordering archetypal ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ (LSCO) system for $x=0.085$. contrast previous reports, LSCO is only short range an in-plane correlation length $\ensuremath{\sim}10\text{ }\text{...
We report an angle-resolved photoemission study of the electronic structure pseudogap state in La1.48Nd0.4Sr0.12CuO4 (Tc<7 K). Two opposite dispersing Fermi arcs are main result this study. Several scenarios that can explain observation discussed.
The existence of coherent quasiparticles near the Fermi energy in low temperature state high-temperature superconductors has been well established by angle-resolved photoemission spectroscopy (ARPES). This technique directly probes momentum-resolved electronic excitation spectrum CuO$_2$ planes. We present a study close to optimally doped La$_{1.83}$Sr$_{0.17}$CuO$_4$ superconducting and report an abrupt change quasiparticle spectral function, as we follow dispersion ARPES signal from up 0.6...
We used polarized inelastic neutron-scattering measurements to shed light on the spin-lattice quantum entanglement in multiferroic materials. report an evidence for hybrid elementary excitations made of a mixing between spin waves and phonons, which can be considered as Goldstone modes. argue that Dzyaloshinskii-Moriya interaction could at origin this hybridization.
Inelastic neutron-scattering experiments on the high-temperature superconductor ${\mathrm{La}}_{1.855}{\mathrm{Sr}}_{0.145}{\mathrm{CuO}}_{4}$ reveal a magnetic excitation gap $\ensuremath{\Delta}$ that decreases continuously upon application of field perpendicular to ${\mathrm{CuO}}_{2}$ planes. The vanishes at critical required induce long-range incommensurate antiferromagnetic order, providing compelling evidence for field-induced soft-mode driven quantum phase transition.
We present inelastic neutron scattering data on highly overdoped ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ single crystals with superconducting transition temperature ${T}_{C}=70\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and, for comparison, a nearly optimally doped crystal ${T}_{C}=87\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. In both samples, magnetic resonant modes odd and even symmetry under exchange of the two...