A5002807575- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Theoretical and Computational Physics
- Iron-based superconductors research
- Magnetic and transport properties of perovskites and related materials
- Magnetic properties of thin films
- Rare-earth and actinide compounds
- High-pressure geophysics and materials
- Superconducting Materials and Applications
- Superconductivity in MgB2 and Alloys
- Seismic Waves and Analysis
- Geomagnetism and Paleomagnetism Studies
- Fluid Dynamics and Turbulent Flows
- Magneto-Optical Properties and Applications
- Intellectual Capital and Performance Analysis
- Characterization and Applications of Magnetic Nanoparticles
- Quantum and electron transport phenomena
- Lattice Boltzmann Simulation Studies
- Aeolian processes and effects
- Geophysical and Geoelectrical Methods
- Multiferroics and related materials
- Atomic and Subatomic Physics Research
- Magnetic confinement fusion research
- Corporate Taxation and Avoidance
- Magnetic Properties and Applications
Delft University of Technology
2012-2024
Centre National de la Recherche Scientifique
2013-2022
Université Paris-Saclay
2016-2022
Centre de Nanosciences et de Nanotechnologies
2017-2022
École Polytechnique
2010-2020
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2009-2020
CEA Paris-Saclay
2016-2020
Netherlands Forensic Institute
2015-2019
Université Paris-Sud
2019
Laboratoire des Solides Irradiés
2005-2017
The theory for thermally assisted flux flow (TAFF) in the limit of small driving forces is used to derive exact expressions time-dependent behaviour magnetisation and permeability. problem especially relevant high-temperature superconductors where large variations transition temperature DC fields are observed as a function frequency probing AC field. parameters extensively discussed relation present understanding pinning.
In layered superconductors with very weak coupling between the layers concept of a flux-line lattice breaks down when field is oriented parallel to superconducting planes. For an arbitrary orientation we propose that formation Abrikosov only related perpendicular component. The component penetrates as if planes were completely decoupled. This model explains recent experiments which have questioned driving mechanism for dissipation in phase high-temperature oxide superconductors.
Detailed measurements of the critical current density jc YBa2Cu3O7 films grown by pulsed laser deposition reveal increase as function filmthickness. Both this thickness dependence and field are consistently described using a generalization theory strong pinning Ovchinnikov Ivlev [Phys. Rev. B 43, 8024 (1991)]. From model, we deduce values defect (10^21 m^-3) elementary force, which in good agreement with generally accepted for Y2O3-inclusions. In absence clear evidence that is determined...
We present direct evidence of a "peak effect" as precursor to vortex lattice melting in single crystal $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ containing only two twin planes. The peak effect occurs just below the liquid solid phase transition narrow field region between 0.3 and 1.5 T for $H\ensuremath{\parallel}\mathbf{c}$ is clearly observed function both magnetic temperature. demonstrate that due enhanced pinning by boundaries,...
We report high-sensitivity microwave measurements of the in-plane penetration depth ${\ensuremath{\lambda}}_{ab}$ and quasiparticle scattering rate $1/\ensuremath{\tau}$ in several single crystals hole-doped Fe-based superconductor ${\mathrm{Ba}}_{1\ensuremath{-}x}{\mathrm{K}}_{x}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ ($x\ensuremath{\approx}0.55$). While a power-law temperature dependence with power $\ensuremath{\sim}2$ is found large $1/\ensuremath{\tau}$, we observe an exponential superfluid...
The response of the vortex system in mixed state type-II superconductors to ac fields is discussed from a unique macroscopic point view. Linear and nonlinear are derived as two opposite limits same diffusionlike equation for magnetic flux. susceptibility experiments carried out limit strong nonlinearity entirely equivalent magnetic-relaxation or field-ramp experiments. magnitude frequency dependence threshold, amplitude field where one crosses essentially linear strongly response, found both...
We have investigated the possible role of two-dimensional vortex-lattice defects in thermally assisted flux flow for very anisotropic high-temperature superconductor ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$ (Bi-Sr-Ca-Cu-O). At low current densities, this mechanism, which we shall refer to as plastic creep, is expected prevail over creep elastically correlated bundles, or elastic creep. It assumed that vortices are pinned by...
We report on the temperature and field dependencies of resistivity an untwinned $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ single crystal before after 1 MeV electron irradiation in fields up to 8 T. show, for first time, direct suppression order vortex liquid-to-solid phase transition due controlled introduction point defects, that transport liquid is dominated by viscosity rather than pinning. Furthermore, we demonstrate can be recovered...
Magnetization measurements in field on a ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8}$ single crystal do not reveal any sharp phase transition between the normal and superconducting states. The M(H) curves for temperatures about ${\mathit{T}}_{\mathit{c}}$ fields up to 5 T all display diamagnetic behavior. Above mean-field temperature ${\mathit{T}}_{\mathit{c}}^{\mathrm{MF}}$, quasi-two-dimensional fluctuations are responsible. Below...
Ultrasound velocity measurements of the unconventional superconductor ${\mathrm{CeCoIn}}_{5}$ with extremely large Pauli paramagnetic susceptibility reveal an unusual structural transformation flux-line lattice (FLL) in vicinity upper critical field. The transition field coincides that at which heat capacity a second-order phase transition. lowering sound is consistent vortex segmentation and crossover to quasi-two-dimensional FLL pinning. These results provide strong evidence high-field...
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...
Time-resolved local induction measurements near the vortex lattice order-disorder transition in optimally doped ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ crystals show that high-field, disordered phase can be quenched to fields as low half field. Over an important range of fields, electrodynamical behavior system is governed by coexistence ordered and phases sample. We interpret results supercooling high-field possible first-order nature at...
The angular dependence of the ac screening ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ single crystals irradiated with 5.8 GeV Pb ions is used to demonstrate importance interactions between vortex segments in different Cu${\mathrm{O}}_{2}$ layers. field tilt angle below which pinning by columnar defects effective very large: ${\ensuremath{\Theta}}_{a}\ensuremath{\approx}70\ifmmode^\circ\else\textdegree\fi{}$. magnitude and frequency...
Charge doping of iron-pnictide superconductors leads to collective pinning flux vortices, whereas isovalent does not. Moreover, in the charge-doped compounds is consistently described by mean-free path fluctuations introduced dopant atoms, allowing for extraction elastic quasiparticle scattering rate. The absence atoms isovalently doped ${\mathrm{BaFe}}_{2}({\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x}{)}_{2}$ consistent with observation a linear temperature dependence low-temperature...
We measured the heat capacity C(p) and microwave surface impedance Z(s) in vortex state of YNi2B2C. In contrast to conventional s-wave superconductors, shows a square root[H] dependence. This dependence persists even after introduction columnar defects which change electronic structure core regime destroy regular lattice. On other hand, flux flow resistivity is nearly proportional H. These results indicate that YNi2B2C fundamentally different from counterparts, delocalized quasiparticle...
The authors have grown single crystals of Bi2Sr2CaCu2O8 and measured their DC magnetisation (using both SQUID Foner magnetometers) AC susceptibility in small magnetic fields. They find a flux expulsion fraction up to 34% the shielding effect fields down 3 G, significantly larger than found for YBa2Cu3O7 crystals. Critical currents were determined as function temperature by applying Bean's model are compared with critical single-crystal YBa2Cu3O7. current densities strongly dependent on field...
We have studied the lower critical fields ${H}_{c1}$ of superconducting iron oxipnictide ${\text{PrFeAsO}}_{1\ensuremath{-}y}$ single crystals for $\mathbit{H}$ parallel and perpendicular to $ab$ planes. Measurements local magnetic induction at positions straddling sample edge by using a miniature Hall-sensor array clearly resolve first flux penetration from Meissner state. The temperature dependence $\mathbit{H}\ensuremath{\parallel}c$ is well scaled in-plane depth without showing any...
The frequency-dependent shielding of an applied ac field is used to study the vortex dynamics in a ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8}$ single crystal irradiated with 5.8-GeV Pb ions. At fields below matching ${\mathit{B}}_{\mathrm{\ensuremath{\Phi}}}$\ensuremath{\approxeq}200 G, sample exhibits strong pinning due irradiation-induced columnar defects. this regime shown be accurate agreement predictions Bose-glass theory Nelson and Vinokur [Phys. Rev....