27 research outputs found
Galvanomagnetic properties and noise in a barely metallic film of V2O3
We have measured the magnetotransport properties of a strained metallic V2O3
thin film. Most of the properties are similar to V2O3 single crystals that have
been submitted to a large pressure. In addition, resistance noise analysis
indicates that conductivity fluctuations are freezing out at T\approx 10K.
Examination of a range of measurements leads to the conclusion that
spins-configuration fluctuations dominate in the low temperature regime.Comment: accepted for publication in Phys Rev
Charge Density Wave and Superconducting Properties in Single Crystals of Lu5Ir4Si10
We measured the electrical resistivity from 2K up to 900K on high quality
single crystals of Lu5Ir4Si10. A clear thermal hysteresis was found at the
onset of the Charge Density Wave (CDW), evidencing the first order nature of
the transition. When tantalum is included in the compound, the CDW is destroyed
and the superconducting critical temperature is enhanced. Finally, we present
specific heat and magnetic penetration depth in the Meissner state. We show
that the superconducting properties are very close to a weak coupling BCS
superconductor
Superconducting nano-mechanical diamond resonators
In this work we present the fabrication and characterization of
superconducting nano-mechanical resonators made from nanocrystalline boron
doped diamond (BDD). The oscillators can be driven and read out in their
superconducting state and show quality factors as high as 40,000 at a resonance
frequency of around 10 MHz. Mechanical damping is studied for magnetic fields
up to 3 T where the resonators still show superconducting properties. Due to
their simple fabrication procedure, the devices can easily be coupled to other
superconducting circuits and their performance is comparable with
state-of-the-art technology.Comment: 5 pages 6 figures, Accepted for publication in Carbo
Scanning tunneling spectroscopy with superconducting tips of Al
International audienceWe present scanning tunneling spectroscopy measurements at 0.1 K using tips made of Al. At zero field, the atomic lattice and charge density wave of 2H-NbSe2 are observed, and under magnetic fields the peculiar electronic properties of vortices are precisely resolved. The tip density of states is influenced by the local magnetic field of the vortex, providing a new probe for the magnetic field at nanometric sizes
Penetration depth study of superconducting gap structure of 2H-NbSe2
International audienceWe report measurements of the temperature dependence of both in-plane and out-of-plane penetration depths (lambda(a) and lambda(c) respectively) in 2H-NbSe2. Measurements were made with a radio-frequency tunnel diode oscillator circuit at temperatures down to 100 mK. Analysis of the anisotropic superfluid density shows that a reduced energy gap is located on one or more of the quasi-two-dimensional Nb Fermi surface sheets rather than on the Se sheet, in contrast with some previous reports. This result suggests that the gap structure is not simply related to the weak electron-phonon coupling on the Se sheet and is therefore important for microscopic models of anisotropic superconductivity in this compound
Anisotropic superconductivity in NbSe2 probed by magnetic penetration depth
International audienceNbSe2 shows coexistence of a charge density wave (TCDW similar to 32 K) with a superconducting state below T = 7.2 K. Recent ARPES measurements revealed different values of the superconducting gap on the main sheets of the Fermi surface. These results suggest a multigap superconductivity such as in MgB2. The temperature dependence of the magnetic penetration depth (;.(T)) down to T,11 6 has been measured on high quality single crystals in the Meissner state. A strong increase of the in-plane penetration depth is observed, signaling the presence of low lying excitations. Given the relative contributions of each Fermi surface sheet, these measurements indicate that a reduced gap is not necessarily only found on the small Se sheet as suggested by the ARPES measurements. These results are discussed in a framework of multigap superconductivity
Explorar e Investigar em Matemática: Uma Actividade Fundamental no Ensino e na Aprendizagem
Investigar, ensinar e aprender são actividades que podem estar presentes, de forma
articulada, no ensino-aprendizagem da Matemática e na actividade profissional do
professor. Para isso, é necessário conceber tarefas que possam ser o ponto de partida para
investigações e explorações matemáticas dos alunos e discutir o modo como podem ser
trabalhadas na sala de aula. Recorrendo a exemplos de actividades realizadas por
professores de Matemática portugueses, analiso a actividade de aprendizagem suscitada
por tarefas deste tipo e discuto as respectivas potencialidades. Finalmente, refiro as
condições respeitantes à cultura profissional dos professores que podem favorecer uma
actividade de investigação sobre a sua própria profissional, com relevo para a colaboração
e a dimensão associativa.Researching, teaching and learning are activities that may be present, in coordination,
teaching and learning of mathematics in the work of the teacher. Therefore, it is necessary
to design tasks that may be the starting point for mathematical investigations and
explorations of the students and discuss how they can be worked in the classroom. Drawing
on examples of activities carried out by Portuguese teachers of mathematics by examining
the activity of learning raised by such tasks and discuss their potencial. Finally, I refer to
conditions relating to the professional culture of teachers who can promote the research
activity on their own training, with an emphasis on collaboration and associative dimension
Genetic markers in clinical subtypes of juvenile idiopathic arthritis
Poster presentatationInternational audienc