Laboratory of Solid State Physics

About: Laboratory of Solid State Physics is a facility organization based out in Orsay, France. It is known for research contribution in the topics: Graphene & Scanning tunneling microscope. The organization has 622 authors who have published 666 publications receiving 17444 citations.

SrTi O 3 : An intrinsic quantum paraelectric below 4 K

Abstract: The dielectric constants ${\ensuremath{\epsilon}}_{〈110〉}$ and their change with uniaxial $〈1\overline{1}0〉$ stress in monodomain $〈001〉$SrTi${\mathrm{O}}_{3}$ samples have been measured as a function of temperature. Between 4 K and 0.3 K these quantities are independent of temperature. In one sample $\ensuremath{\epsilon}(T)$ was measured to 0.035 K and found to be constant. This proves the quantum-mechanical stabilization of the paraelectric phase below 4 K with a very high dielectric constant $\ensuremath{\epsilon}$. The crossover from classical to quantum behavior on lowering the temperature is discussed, and it is shown that the coupling of the ferroelectric mode to acoustic ones is important. The $\ensuremath{\epsilon}(T)$ dependence is compared to earlier and recent theories. The former, yielding a coth ($\frac{\ensuremath{\hbar}\ensuremath{\Omega}}{\mathrm{kT}}$) term, are found to be inadequate for the crossover region. A recent biquadratic ferroelectric mode-coupling theory fits the data better.

Synthesis of few-layer graphene via microwave plasma-enhanced chemical vapour deposition

Abstract: If graphene is ever going to live up to the promises of future nanoelectronic devices, an easy and cheap route for mass production is an essential requirement. A way to extend the capabilities of plasma-enhanced chemical vapour deposition to the synthesis of freestanding few-layer graphene is presented. Micrometre-wide flakes consisting of four to six atomic layers of stacked graphene sheets have been synthesized by controlled recombination of carbon radicals in a microwave plasma. A simple and highly reproducible technique is essential, since the resulting flakes can be synthesized without the need for a catalyst on the surface of any substrate that withstands elevated temperatures up to 700 °C. A thorough structural analysis of the flakes is performed with electron microscopy, x-ray diffraction, Raman spectroscopy and scanning tunnelling microscopy. The resulting graphene flakes are aligned vertically to the substrate surface and grow according to a three-step process, as revealed by the combined analysis of electron microscopy and x-ray photoelectron spectroscopy.

Neurotoxicity of Alzheimer's disease Aβ peptides is induced by small changes in the Aβ42 to Aβ40 ratio.

Abstract: The amyloid peptides Aβ(40) and Aβ(42) of Alzheimer's disease are thought to contribute differentially to the disease process. Although Aβ(42) seems more pathogenic than Aβ(40), the reason for this is not well understood. We show here that small alterations in the Aβ(42):Aβ(40) ratio dramatically affect the biophysical and biological properties of the Aβ mixtures reflected in their aggregation kinetics, the morphology of the resulting amyloid fibrils and synaptic function tested in vitro and in vivo. A minor increase in the Aβ(42):Aβ(40) ratio stabilizes toxic oligomeric species with intermediate conformations. The initial toxic impact of these Aβ species is synaptic in nature, but this can spread into the cells leading to neuronal cell death. The fact that the relative ratio of Aβ peptides is more crucial than the absolute amounts of peptides for the induction of neurotoxic conformations has important implications for anti-amyloid therapy. Our work also suggests the dynamic nature of the equilibrium between toxic and non-toxic intermediates.