A5056291125- Physics of Superconductivity and Magnetism
- Superconductivity in MgB2 and Alloys
- Iron-based superconductors research
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Rare-earth and actinide compounds
- Theoretical and Computational Physics
- Thermal Expansion and Ionic Conductivity
- Quantum and electron transport phenomena
- High-pressure geophysics and materials
- Diamond and Carbon-based Materials Research
- Superconducting Materials and Applications
- Probabilistic and Robust Engineering Design
- Quasicrystal Structures and Properties
- Magnetic properties of thin films
- Statistical Methods and Inference
- Advanced Materials Characterization Techniques
- Organic and Molecular Conductors Research
- Surface and Thin Film Phenomena
- Magnetic Properties of Alloys
- Advanced Statistical Methods and Models
- Geomagnetism and Paleomagnetism Studies
- Electronic and Structural Properties of Oxides
- Semiconductor materials and interfaces
- Microwave Dielectric Ceramics Synthesis
Institut Néel
2015-2025
Centre National de la Recherche Scientifique
2015-2025
Université Grenoble Alpes
2015-2025
Institut Superieur de l'Aeronautique et de l'Espace (ISAE-SUPAERO)
2024
École Nationale de l’Aviation Civile
2018-2024
Institut de Mathématiques de Toulouse
2011-2024
Université Toulouse III - Paul Sabatier
2022-2024
Institut National des Sciences Appliquées de Toulouse
2022-2024
Institut polytechnique de Grenoble
2018-2023
Université Joseph Fourier
2003-2014
Experimental support is found for the multiband model of superconductivity in recently discovered system MgB(2) with transition temperature T(c) = 39 K. By means Andreev reflection, evidence obtained two distinct superconducting energy gaps. The sizes gaps ( Delta(S) 2.8 meV and Delta(L) 7 meV) are, respectively, smaller larger than expected weak coupling value. Because smearing spectra are hardly distinguishable at elevated temperatures, but when a magnetic field applied presence can be...
The recently discovered superconductor UTe$_2$, with a T$_c$ between 1.5~K and 2~K, is attracting much attention due to strong suspicion of spin-triplet topological superconductivity. Its properties under magnetic field are also remarkable, field-reinforced field-induced superconducting phases. Here, we report the first complete thermodynamic determination phase diagram for fields applied along three crystallographic directions. Measurements were performed up 36~T hard magnetisation $b$~axis...
Homoepitaxial diamond layers doped with boron in the 10(20)-10(21) cm(-3) range are shown to be type II superconductors sharp transitions (approximately 0.2 K) at temperatures increasing from 0 2.1 K contents. The critical concentration for onset of superconductivity those 001-oriented single-crystalline films is about 5-7 10(20) cm(-3). H-T phase diagram has been obtained transport and ac-susceptibility measurements down 300 mK.
We report on specific heat, high magnetic field transport and $ac-$susceptibility measurements magnesium diboride single crystals. The upper critical $H_{c2}$ for fields perpendicular parallel to the Mg B planes is presented first time in entire temperature range. A very different dependence has been observed two directions which yields a dependent anisotropy with $\Gamma \sim$ 5 at low temperatures about 2 near $T_c$. peak effect susceptibility $H \sim $2 T $c-$axis current density presnts...
Local magnetic measurements are used to quantitatively characterize heterogeneity and flux line pinning in ${\text{PrFeAsO}}_{1\ensuremath{-}y}$ NdFeAs(O,F) superconducting single crystals. In spite of spatial fluctuations the critical current density on macroscopic scale, it is shown that major contribution comes from collective vortex lines by microscopic defects mean-free-path fluctuation mechanism. The defect extracted experiment corresponds dopant atom density, which means atoms play an...
We present here the first results on transport and magnetic properties in new stable icosahedral Al1-x-yPdxMny phases (x/y = 22/7.5, 21/8.5, 19/10). These melt-spun samples are of high structural quality even as-quenched state high-resistivity values which depend strongly nominal composition with ρ4K ∼ 10 000 μΩ cm annealed Al70.5Pd22Mn7.5 1600 Al71Pd19Mn10. Moreover system becomes more diamagnetic as its resistivity increases.
The temperature dependence of the upper (${H}_{c2}$) and lower (${H}_{c1}$) critical fields has been deduced from Hall probe magnetization measurements high quality ${\mathrm{M}\mathrm{g}\mathrm{B}}_{2}$ single crystals along two main crystallographic directions. We show that ${\ensuremath{\Gamma}}_{{H}_{c2}}={H}_{c2\ensuremath{\parallel}ab}/{H}_{c2\ensuremath{\parallel}c}$ ${\ensuremath{\Gamma}}_{{H}_{c1}}={H}_{c1\ensuremath{\parallel}c}/{H}_{c1\ensuremath{\parallel}ab}$ differ...
The introduction of crystalline defects or dopants can give rise to so-called "dirty superconductors", characterized by reduced coherence length and quasiparticle mean free path. In particular, granular superconductors such as Granular Aluminum (GrAl), consisting remarkably uniform grains connected Josephson contacts have attracted interest since the sixties thanks their rich phase diagram practical advantages, like increased critical temperature, field, kinetic inductance. Here we report...
We report on a detailed study of the optical response and ${T}_{c}\text{\ensuremath{-}}\ensuremath{\rho}$ phase diagram (${T}_{c}$ being superconducting critical temperature $\ensuremath{\rho}$ normal state resistivity film) granular aluminum, combining transport measurements high resolution spectroscopy technique. The is discussed as resulting from an interplay between stiffness, Coulomb repulsion, gap $\mathrm{\ensuremath{\Delta}}$. provide direct evidence for two different types well...
The specific heat $C$ of the cuprate superconductors La$_{2-x}$Sr$_x$CuO$_4$ and Bi$_{2+y}$Sr$_{2-x-y}$La$_x$CuO$_{6+\delta}$ was measured at low temperature (down to $0.5~{\rm K}$), for dopings $p$ close $p^\star$, critical doping onset pseudogap phase. A magnetic field up $35~{\rm T}$ applied suppress superconductivity, giving direct access normal state temperature, enabling a determination $C_e$, electronic contribution normal-state heat, $T \to 0$. In $x=p = 0.22$, $0.24$ $0.25$, $C_e /...
The superconducting phase diagram of MgB2 was determined from magnetization, magneto-transport and the first single-crystal specific heat measurements. A zero-temperature in-plane coherence length 8 nm is determined. anisotropy increases a value around 2 near Tc to above 4.5 at 22 K. For H||c pronounced peak effect in critical current occurs upper field. Evidence for surface state presented which might account wide spread reported values anisotropy.
The heat capacity of a $2{\text{H-NbS}}_{2}$ single crystal has been measured by highly sensitive ac technique down to 0.6 K and in magnetic fields up 14 T. At very low temperatures, data show excitations over an energy gap $(2{\ensuremath{\Delta}}_{S}/{k}_{B}{T}_{c}\ensuremath{\approx}2.1)$ much smaller than the BCS value. overall temperature dependence electronic specific ${C}_{e}$ can be explained either existence strongly anisotropic single-energy or within two-gap scenario with large...
A new calorimeter for measurements of the heat capacity and magnetocaloric effect small samples in pulsed magnetic fields is discussed exploration thermal thermodynamic properties at temperatures down to 2 K. We tested method up μ0H=50 T, but it could be extended higher fields. For these we used carefully calibrated bare-chip Cernox® RuO2 thermometers, present a comparison their performances. The monotonic temperature field dependences magnetoresistance allow thermometry with precision as...
We present a detailed study of the temperature ($T$) and magnetic field ($H$) dependence electronic density states (DOS) at Fermi level, as deduced from specific heat Knight shift measurements in underdoped ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$. find that DOS becomes independent above characteristic ${H}_{\mathrm{DOS}}$, ${H}_{\mathrm{DOS}}(T)$ line displays an unusual inflection near onset long-range 3D charge-density wave order. The $S$ shape is suggestive two mutually...
The upper and lower critical fields have been deduced from specific heat Hall-probe magnetization measurements in nonoptimally doped Nd(O,F)FeAs single crystals $({T}_{c}\ensuremath{\sim}32--35\text{ }\text{K})$. anisotropy of the penetration depth $({\ensuremath{\Gamma}}_{\ensuremath{\lambda}})$ is temperature independent on order $4.0\ifmmode\pm\else\textpm\fi{}1.5$. Similarly specific-heat data lead to an coherence length...
Ising superconductivity allows in-plane upper critical magnetic fields to vastly surpass Pauli limit by locking the antiparallel electron spins of Cooper pairs in out-of-plane direction. It was first explicitly demonstrated fully two-dimensional monolayers transition metal dichalcogenides with large spin-orbit coupling and broken inversion symmetry. Since then, several studies have shown that it can be present layered bulk materials, too. In our previous study, we clarified underlying...
The recent discovery of a charge order in underdoped YBa2Cu3Oy raised the question interplay between superconductivity and this competing phase. Understanding normal state high-temperature superconductors is now an essential step towards description pairing mechanism those materials determining upper critical field therefore fundamental importance. We present here calorimetric determination field-temperature phase diagram single crystals. show that specific heat saturates high magnetic...
The angular dependence of the upper critical field ${H}_{c2}$ ${\mathrm{MgB}}_{2}$ single crystals is studied at various temperatures by means specific-heat and transport measurements in magnetic fields up to $17\phantom{\rule{0.3em}{0ex}}\mathrm{T}$. Clear deviations from Ginzburg--Landau behavior are observed all explained two-band effects. temperature qualitative agreement with theoretical predictions based on band-structure calculations. Quantitative obtained an interband coupling...