511 research outputs found
Pressure Effect and Specific Heat of RBa2Cu3Ox at Distinct Charge Carrier Concentrations: Possible Influence of Stripes
In YBa2Cu3Ox, distinct features are found in the pressure dependence of the
transition temperature, dTc/dp, and in DeltaCp*Tc, where DeltaCp is the jump in
the specific heat at Tc: dTc/dp becomes zero when DeltaCp*Tc is maximal,
whereas dTc/dp has a peak at lower oxygen contents where DeltaCp*Tc vanishes.
Substituting Nd for Y and doping with Ca leads to a shift of these specific
oxygen contents, since oxygen order and hole doping by Ca influences the hole
content nh in the CuO2 planes. Calculating nh from the parabolic Tc(nh)
behavior, the features coalesce for all samples at nh=0.11 and nh=0.175,
irrespective of substitution and doping. Hence, this behavior seems to reflect
an intrinsic property of the CuO2 planes. Analyzing our results we obtain
different mechanisms in three doping regions: Tc changes in the optimally doped
and overdoped region are mainly caused by charge transfer. In the slightly
underdoped region an increasing contribution to dTc/dp is obtained when well
ordered CuO chain fragments serve as pinning centers for stripes. This behavior
is supported by our results on Zn doped NdBa2Cu3Ox and is responsible for the
well known dTc/dp peak observed in YBa2Cu3Ox at x=6.7. Going to a hole content
below nh=0.11 our results point to a crossover from an underdoped
superconductor to a doped antiferromagnet, changing completely the physics of
these materials.Comment: 6 pages, 5 figures Proccedings of the 'Stripes 2000' Conference, Rome
(2000
Reentrant vortex lattice transformation in four-fold symmetric superconductors
The physics behind the rhombicsquarerhombic flux line lattice
transformation in increasing fields is clarified on the basis of Eilenberger
theory. We demonstrate that this reentrance observed in LuNiBC is due
to intrinsic competition between superconducting gap and Fermi surface
anisotropies. The calculations reproduce not only it but also predict yet not
found lock-in transition to a square lattice with different orientation in
higher field. In view of physical origin given, this sequence of transitions is
rather generic to occur in four-fold symmetric superconductors.Comment: 5 pages, 4 figures,submitted to Phys. Rev. Let
Case study: ENVRI science demonstrators with D4Science
Whenever a community of practice starts developing an IT solution for its use case(s) it has to face the issue of carefully selecting “the platform” to use. Such a platform should match the requirements and the overall settings resulting from the specific application context (including legacy technologies and solutions to be integrated and reused, costs of adoption and operation, easiness in acquir- ing skills and competencies). There is no one-size-fits-all solution that is suitable for all application context, and this is particularly true for scientific communities and their cases because of the wide heterogeneity characterising them. However, there is a large consensus that solutions from scratch are inefficient and services that facilitate the development and maintenance of scientific community-specific solutions do exist. This chapter describes how a set of diverse communities of practice efficiently developed their science demonstrators (on analysing and pro- ducing user-defined atmosphere data products, greenhouse gases fluxes, particle formation, mosquito diseases) by leveraging the services offered by the D4Science infrastructure. It shows that the D4Science design decisions aiming at streamlin- ing implementations are effective. The chapter discusses the added value injected in the science demonstrators and resulting from the reuse of D4Science services, especially regarding Open Science practices and overall quality of service
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