A5109054782- Physics of Superconductivity and Magnetism
- Superconductivity in MgB2 and Alloys
- Iron-based superconductors research
- Advanced Condensed Matter Physics
- High-pressure geophysics and materials
- Magnetic and transport properties of perovskites and related materials
- Rare-earth and actinide compounds
- Magnetic properties of thin films
- Thermal Expansion and Ionic Conductivity
- Theoretical and Computational Physics
- Corporate Taxation and Avoidance
- GaN-based semiconductor devices and materials
- Boron and Carbon Nanomaterials Research
- Magnetic Properties of Alloys
- Magnesium Alloys: Properties and Applications
- Nuclear materials and radiation effects
- Intellectual Capital and Performance Analysis
- Acoustic Wave Resonator Technologies
- Inorganic Fluorides and Related Compounds
- Semiconductor materials and devices
- Superconducting Materials and Applications
- ZnO doping and properties
- Chemical and Physical Properties of Materials
- Surface and Thin Film Phenomena
- Semiconductor Quantum Structures and Devices
École Polytechnique Fédérale de Lausanne
1994-2017
ETH Zurich
2007-2016
Uniwersytet Komisji Edukacji Narodowej w Krakowie
2014-2015
Solid State Physics Laboratory
2001-2010
Technische Universität Braunschweig
2008
KU Leuven
2000
Analytisches Laboratorium
1989-1997
University of Zurich
1995-1997
IBM Research - Zurich
1993-1994
Board of the Swiss Federal Institutes of Technology
1992-1994
The anisotropy gamma of the superconducting state high quality single crystals MgB2 was determined, using torque magnetometry with two different methods. upper critical field found to be temperature dependent, decreasing from approximately 6 at 15 K 2.8 35 K. Reversible data near T(c) reveal a dependent anisotropy, increasing nearly linearly equal 2 in zero 3.7 10 kOe. unusual dependence is true bulk property and can explained by nonlocal effects anisotropic pairing and/or k--> effective mass tensor.
The anisotropic resistivity components of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{4}$${\mathrm{O}}_{8}$ have been measured from 0 to 900 K. is an underdoped, genuinely untwinned, and stoichiometric high temperature superconductor. ${\mathrm{CuO}}_{2}$ plane ${\mathrm{\ensuremath{\rho}}}_{\mathit{a}}$ exhibits a strong correlation with the spin dynamics, i.e., Knight shift spin-lattice relaxation time ${\mathit{T}}_{1}$. along b axis (plane plus chain) consistent Bloch-Gr\"uneisen theory....
We report scanning tunneling spectroscopy imaging of the vortex lattice in single crystalline MgB2. By parallel to c axis, a superconducting gap (Delta=2.2 meV) associated with pi band is observed. The vortices have large core size compared estimates based on H(c2) and show an absence localized states core. Furthermore, superconductivity between rapidly suppressed by applied field. These results suggest that is, at least partially, induced intrinsically sigma band.
We demonstrate the existence of a novel superconducting state in high quality two-component ${\mathrm{MgB}}_{2}$ single crystalline superconductors where unique combination both type-1 (${\ensuremath{\lambda}}_{1}/{\ensuremath{\xi}}_{1}<1/\sqrt{2}$) and type-2 (${\ensuremath{\lambda}}_{2}/{\ensuremath{\xi}}_{2}>1/\sqrt{2}$) superconductor conditions is realized for two components order parameter. This condition leads to vortex-vortex interaction attractive at long distances repulsive short...
We present the results of first directional point-contact spectroscopy experiments in high-quality ${\mathrm{M}\mathrm{g}\mathrm{B}}_{2}$ single crystals. Because directionality current injection into samples, application a magnetic field allowed us to separate contributions $\ensuremath{\sigma}$ and $\ensuremath{\pi}$ bands total conductance our point contacts. By using this technique, we were able obtain temperature dependency each gap independent other. The consequent, strong reduction...
Growth of carbon substituted magnesium diboride Mg(B1-xCx)2 single crystals with 0<x<0.15 is reported and the structural, transport, magnetization data are presented. The superconducting transition temperature decreases monotonically increasing content in full investigated range substitution. By adjusting nominal composition, Tc can be tuned a wide between 10 39 K. Simultaneous introduction disorder by substitution significant increase upper critical field Hc2 observed. Comparing...
The first direct observation of charge order Ni(3+delta(')) and Ni(3-delta) by resonant x-ray scattering experiments in an epitaxial film NdNiO3 is reported. A quantitative value delta+delta(') = (0.45 +/- 0.04)e was obtained. temperature dependence the deviates significantly from those magnetic moment crystallographic structure. This might be indication a difference their fluctuation time scales. These observations are discussed terms temperature-driven metal-insulator transition RNiO3 family.
The ab-plane thermal conductivity $\kappa$ of single-crystalline hexagonal MgB_2 has been measured as a function magnetic field H with orientations both parallel and perpendicular to the c-axis at temperatures between 0.5 300 K. In mixed state, $\kappa(H)$ constant reveals features that are not typical for common type-II superconductors. observed behavior may be associated field-induced reduction two superconducting energy gaps, significantly different in magnitude. A nonlinear temperature...
We measure phonon dispersion and linewidth in a single crystal of MgB2 along the Gamma-A, Gamma-M, A-L directions using inelastic x-ray scattering. use density functional theory to compute effect both electron-phonon coupling anharmonicity on linewidth, obtaining excellent agreement with experiment. Anomalous broadening E(2g) mode is found all Gamma-A. The dominant contribution always coupling.
We report on measurements of the magnetic moment in superconducting MgB2 single crystals. find \mu_0H_{c2}^c(0) = 3.2 T, \mu_0H_{c2}^{ab}(0) 14.5 \gamma 4.6, \mu_0H_c(0) 0.28 and \kappa(T_c) 4.7. The standard Ginzburg-Landau London model relations lead to a consistent data set indicate that is clean limit superconductor intermediate coupling strength with very pronounced anisotropy effects.
Single crystals of SmFeAsO1−xFy a size up to 120 × 100 µm2 have been grown from NaCl/KCl flux at pressure 30 kbar and temperature 1350–1450 °C using the cubic anvil high-pressure technique. The superconducting transition obtained single varies between 45 53 K. Obtained are characterized by full diamagnetic response in low magnetic fields high critical current density fields. Structural refinement has performed on crystal. Differential thermal analysis investigations 1 bar Ar show...
We report observation of Leggett's collective mode in a multiband MgB2 superconductor with Tc=39 K arising from the fluctuations relative phase between two superconducting condensates. The novel is observed by Raman spectroscopy at 9.4 meV fully symmetric scattering channel. frequency consistent theoretical considerations based on first-principles computations.
The in-plane magnetic penetration depth ${\ensuremath{\lambda}}_{ab}$ of the iron selenide superconductor with nominal composition ${\text{FeSe}}_{0.85}$ was studied by means muon-spin rotation. measurements ${\ensuremath{\lambda}}_{ab}^{\ensuremath{-}2}(T)$ are inconsistent a simple isotropic $s$-wave type order parameter but rather in favor two-gap $(s+s)$ and anisotropic symmetries, thus implying that superconducting energy gap contains no nodes.